tag:blogger.com,1999:blog-64122382939760722982017-09-06T15:06:17.019+03:00Electronics PlaygroundElectronics Playground Blog is mainly for sharing information about my projects, teardowns and other stuff related to everything electronic.Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.comBlogger19125tag:blogger.com,1999:blog-6412238293976072298.post-22601994085397017192017-07-20T19:31:00.000+03:002017-07-20T19:31:04.804+03:00My Hi-Fi Raspberry Pi DAC project. The Build Phase<div style="text-align: justify;"><span style="font-size: medium;">&nbsp;</span><span style="font-size: large;">&nbsp; &nbsp;</span><br /><span style="font-size: large;">&nbsp; &nbsp; This is part two of my Raspberry Pi DAC project. If you &nbsp;want to know how this came about, you might want to read <a href="http://electronicsplayground.blogspot.ro/2017/06/my-hi-fi-raspberry-pi-dac-project.html">part one</a></span></div><span style="font-size: medium;"><span style="font-size: small;"><br /></span><span style="font-size: large;">So, the fun begins.</span></span><br /><b style="font-size: x-large;"><span style="font-size: medium;"><br /></span></b><b><span style="font-size: x-large;">The PCB are here!</span></b><br /><span style="font-size: large;"><b><span style="font-size: medium;"><br /></span></b></span><br /><div style="text-align: justify;"><span style="font-size: medium;"><b><span style="font-size: medium;">&nbsp; &nbsp; </span><span style="font-size: large;">&nbsp;Oh, happy day!.</span></b></span></div><br /><div style="text-align: justify;"><span style="font-size: large;">&nbsp; I ordered my PCBs from PCBWay, and they're not half bad. Pads look OK, the footprints for the TPA op-amp, which had me worried a bit, &nbsp;turned out nice and so did the solder mask.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-U86IoLfBK8c/WVELHjYm9II/AAAAAAAADJE/ydKjoUx-9Oc7xzX8eEVjTwnT44jFl0-rwCKgBGAs/s1600/IMAG3571.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://4.bp.blogspot.com/-U86IoLfBK8c/WVELHjYm9II/AAAAAAAADJE/ydKjoUx-9Oc7xzX8eEVjTwnT44jFl0-rwCKgBGAs/s320/IMAG3571.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-JT_l9P3M0l8/WVELHtQZO0I/AAAAAAAADJE/qMVRFejMU3MmM0elZ-2ZWZtp2joBxxAhgCKgBGAs/s1600/IMAG3572.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://3.bp.blogspot.com/-JT_l9P3M0l8/WVELHtQZO0I/AAAAAAAADJE/qMVRFejMU3MmM0elZ-2ZWZtp2joBxxAhgCKgBGAs/s320/IMAG3572.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-Ss-sObWGens/WVEK-NYAcdI/AAAAAAAADJA/kuQtJvxMM9sB-pkJby-JtvlLnjhjOShBwCKgBGAs/s1600/IMAG3569.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://2.bp.blogspot.com/-Ss-sObWGens/WVEK-NYAcdI/AAAAAAAADJA/kuQtJvxMM9sB-pkJby-JtvlLnjhjOShBwCKgBGAs/s320/IMAG3569.jpg" width="320" /></a></div><br /><br /><div style="text-align: justify;"><span style="font-size: large;">Of course, the first thing was to check and see if the PCBs actually fit the Pi....and they do. Phew!</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">Next up for inspection, the PSU boards:</span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-cCEX3memeaI/WWTfW35eNfI/AAAAAAAADOw/RRqJ86aJgR0LYg85DAMtvMLVBAsrXeb6wCKgBGAs/s1600/19726946_1322024737910789_1274677124_o.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="900" height="320" src="https://3.bp.blogspot.com/-cCEX3memeaI/WWTfW35eNfI/AAAAAAAADOw/RRqJ86aJgR0LYg85DAMtvMLVBAsrXeb6wCKgBGAs/s320/19726946_1322024737910789_1274677124_o.jpg" width="180" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-eBS-WviqE3o/WWTfW0jHATI/AAAAAAAADOw/iwVCYdRSrSwPzg55ZTWqC2TDvuJmZLUXQCKgBGAs/s1600/19723808_1322024654577464_1684066645_o.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="900" height="320" src="https://2.bp.blogspot.com/-eBS-WviqE3o/WWTfW0jHATI/AAAAAAAADOw/iwVCYdRSrSwPzg55ZTWqC2TDvuJmZLUXQCKgBGAs/s320/19723808_1322024654577464_1684066645_o.jpg" width="180" /></a></div><br /><div style="text-align: justify;"><span style="font-size: large;">Lovely. Except, this is the last time I order black solder mask. Every speck of dust is visible, the flux residue looks horrible on it and you can't see anything if the light is not at the right angle.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">That being said, let's start assembling these things.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">I don't own a hot air station, but I do have a digital controllable hot air gun. Soldering the PCM5242 was easier that expected and that kinda built up my confidence. But, like always, Murphy stuck out his head and had a say in the soldering of the TPA op-amp.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">Because it only has 2 pads on 2 of its sides, it made it especially difficult to keep it on the pads. Every time I came closer that 10 cm with my hot air gun, it just blew it off my board.</span></div><div style="text-align: justify;"><span style="font-size: large;">It took me about 40 minutes of frustrating work to finally get the TPA to stick and reflow properly.</span></div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ewQLq-UEoB0/WWTgBV9MWTI/AAAAAAAADO4/DH9BI8B9fcIy088SaQL-7HHTySmTHp6ZwCKgBGAs/s1600/IMAG3628.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://1.bp.blogspot.com/-ewQLq-UEoB0/WWTgBV9MWTI/AAAAAAAADO4/DH9BI8B9fcIy088SaQL-7HHTySmTHp6ZwCKgBGAs/s320/IMAG3628.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-egqQv4qOyXQ/WXDTk0RnSxI/AAAAAAAADXM/e9K7FiiJzNwNr09Evnn-EBsAMgyvcEDewCKgBGAs/s1600/DSCN0034.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://3.bp.blogspot.com/-egqQv4qOyXQ/WXDTk0RnSxI/AAAAAAAADXM/e9K7FiiJzNwNr09Evnn-EBsAMgyvcEDewCKgBGAs/s320/DSCN0034.JPG" width="320" /></a></div><br /><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; My method consisted of applying some solder to the QFN package and a little to the pads on the PCB. Garnish everything with tons of rosin flux and voila!</span><br /><span style="font-size: large;">&nbsp;Just be careful, because if there's too much solder on a pin, the surface tension when the it reflows will keep the package from leveling out on the board or leak out and short to adjacent pads, if the part is slighly moved or pressed.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; After checking for shorts on the DAC and op-amp I went on to solder the rest of the components on the Pi hat</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Ygo2GO7oSAA/WWTgKIrEX_I/AAAAAAAADO8/G8wdnNUjsLEZmxf42HdvlGoebXJWB5LVgCKgBGAs/s1600/IMAG3684.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://1.bp.blogspot.com/-Ygo2GO7oSAA/WWTgKIrEX_I/AAAAAAAADO8/G8wdnNUjsLEZmxf42HdvlGoebXJWB5LVgCKgBGAs/s320/IMAG3684.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-kLxsQ_BHDw8/WWTgKMuEyOI/AAAAAAAADO8/La98-3D1q80lheLNbbQzpinU28wKLJnmQCKgBGAs/s1600/IMAG3680.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://4.bp.blogspot.com/-kLxsQ_BHDw8/WWTgKMuEyOI/AAAAAAAADO8/La98-3D1q80lheLNbbQzpinU28wKLJnmQCKgBGAs/s320/IMAG3680.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: justify;"><span style="font-size: large;">Next up, the PSU boards. These have fairly large components, so they were no trouble at all.</span></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-SD2xCX4Aum4/WWTgBWac6wI/AAAAAAAADO4/8CsFj_6VSNcEpjSMa1ChVeFmi1hE0XPDACKgBGAs/s1600/IMAG3574.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://3.bp.blogspot.com/-SD2xCX4Aum4/WWTgBWac6wI/AAAAAAAADO4/8CsFj_6VSNcEpjSMa1ChVeFmi1hE0XPDACKgBGAs/s320/IMAG3574.jpg" width="320" /></a></div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-RC9ZssSjxmE/WWTiQJgNTtI/AAAAAAAADPM/bqYNyIDa48Qz9RDyjzKjJYpgdkXqi6eYgCKgBGAs/s1600/IMAG3565.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://3.bp.blogspot.com/-RC9ZssSjxmE/WWTiQJgNTtI/AAAAAAAADPM/bqYNyIDa48Qz9RDyjzKjJYpgdkXqi6eYgCKgBGAs/s320/IMAG3565.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4rssC_8IZ7c/WWTiQCjVljI/AAAAAAAADPM/3hM7GKF2owApp_VX_-y0BZJqeDZGJ6DCgCKgBGAs/s1600/IMAG3615.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1067" height="320" src="https://1.bp.blogspot.com/-4rssC_8IZ7c/WWTiQCjVljI/AAAAAAAADPM/3hM7GKF2owApp_VX_-y0BZJqeDZGJ6DCgCKgBGAs/s320/IMAG3615.jpg" width="213" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><br />.<br /><div style="text-align: justify;"><b style="font-size: x-large;"><span style="font-size: x-large;">Ups....</span></b></div><br /><div style="text-align: justify;"><span style="font-weight: bold;"><span style="font-size: large;"><br /></span></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; No, this one isn't about an uninterruptible power supply... I just messed up. Some keen-eyed readers (you the few, the proud, the EEs) might have spotted in the schematic (or, if you haven't, you will now) that the DIN pin of the DAC is atually tied to the DIN of the Raspberry Pi. Yeah, that should have been the DOUT pin on the Pi.</span></div><br /><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; The Pi has DIN on pin 38 and DOUT on pin 40. My DAC is tied to pin 38....I can personally guarantee you that this set-up won't work.</span></div><div style="text-align: justify;"><span style="font-size: large;">Why did I mess up? inconsistent data on some Pi pinouts on the web. That and I was too much of an eager beaver to get the board done so I didn't bother &nbsp;to check more than 2 photos online</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; But, like always, I found a nice easy fix for it. I wasn't really &nbsp;in the mood to cut the trace to pin 38, so I lifted and isolated the pad to R14 going to the Pi's DIN, then soldered a wire from the resistor, to pin 40. There. Problem solved.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-W3J36TrXG-A/WV9GJR2kMtI/AAAAAAAADKU/hfR2sENu0K0Wb0_mnbRpymg-iA82uibgwCKgBGAs/s1600/IMAG3705.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://1.bp.blogspot.com/-W3J36TrXG-A/WV9GJR2kMtI/AAAAAAAADKU/hfR2sENu0K0Wb0_mnbRpymg-iA82uibgwCKgBGAs/s320/IMAG3705.jpg" width="320" /></a></div><br /><br /><b><span style="font-size: x-large;">Make-up!!!</span></b><br /><br /><div style="text-align: justify;">&nbsp; &nbsp; <span style="font-size: large;">&nbsp;I've seen enough fancy DACs on Google's searches to instill in me the conviction that I needed to put everything in a nice anodized aluminium case.... minus the blue LEDs. I hate those, but they seem to be on everything these days.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Ok, micro-rant over. So, I had to fit a Rasberry, its own PSU and two oversized linear PSUs.</span></div><div style="text-align: justify;"><span style="font-size: large;">Loca suppliers didn't have &nbsp;the size or look of what I wanted, so I went shopping elsewhere. In France, actually. I mean, they make fancy everything there. Fancy cheese, fancy wine, horrible cider (interesting story here), fancy aluminium cases. Perfect!</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; The&nbsp;<a href="http://www.audiophonics.fr/en/aluminium-boxes-cases/diy-box-dacphono-100-aluminium-291x172x60mm-p-11033.html">case I got</a>&nbsp;was from Audiophonics. I'm in no way affiliated with them, these guys seem to &nbsp;have everything &nbsp;audio and audio related. &nbsp;My case was about 35 Euros and is 280 x 158 x 48 mm (L x W x H) which is just about the right size to get everything squeezed and allow for some cable management. Some might call this luck. I call it engineering.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-gTxbLe9pmGE/WV9FBykOv2I/AAAAAAAADKM/zWlnDB7zLwsA6rOQNhba8YByrQRI5P24gCKgBGAs/s1600/20170706_203822.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://2.bp.blogspot.com/-gTxbLe9pmGE/WV9FBykOv2I/AAAAAAAADKM/zWlnDB7zLwsA6rOQNhba8YByrQRI5P24gCKgBGAs/s320/20170706_203822.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-_sklqh9C7j8/WXDVwNbmESI/AAAAAAAADXc/8KNW3S7t8hYvxLOeviWunJpz0A6zcR4SwCKgBGAs/s1600/IMAG3745.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://3.bp.blogspot.com/-_sklqh9C7j8/WXDVwNbmESI/AAAAAAAADXc/8KNW3S7t8hYvxLOeviWunJpz0A6zcR4SwCKgBGAs/s320/IMAG3745.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-PocVs7albTo/WXDVwEv3waI/AAAAAAAADXc/-MlVDUdbOqw__-06CGNWUhJwaAxh-GUqQCKgBGAs/s1600/20170708_172631.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://2.bp.blogspot.com/-PocVs7albTo/WXDVwEv3waI/AAAAAAAADXc/-MlVDUdbOqw__-06CGNWUhJwaAxh-GUqQCKgBGAs/s320/20170708_172631.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-97_O2D1zT9Q/WV9FB7EAg1I/AAAAAAAADKM/ahzJBCM-1sw6EFaAb1XyHPPrkE9gzFAkwCKgBGAs/s1600/20170706_203919.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://3.bp.blogspot.com/-97_O2D1zT9Q/WV9FB7EAg1I/AAAAAAAADKM/ahzJBCM-1sw6EFaAb1XyHPPrkE9gzFAkwCKgBGAs/s320/20170706_203919.jpg" width="240" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-c1-hnCCzRyc/WV9FB_cm_rI/AAAAAAAADKM/v0T98QQxKHU1LpMF4kZki26eZZRjraurACKgBGAs/s1600/IMAG3751.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://1.bp.blogspot.com/-c1-hnCCzRyc/WV9FB_cm_rI/AAAAAAAADKM/v0T98QQxKHU1LpMF4kZki26eZZRjraurACKgBGAs/s320/IMAG3751.jpg" width="320" /></a></div><br /><div style="text-align: justify;"><span style="font-size: large;">Oh, the feet I also got from Audiophonics. They're just plastic, but they certainly look the part.</span></div><br /><div style="text-align: justify;"><span style="font-size: large; font-weight: bold;"><br /></span></div><span style="font-size: x-large;"><b>Testing, testing... Is this thing on?</b></span><br /><span style="font-size: large;"><br /></span><br /><div style="text-align: justify;"><span style="font-size: large;"><b>&nbsp;</b> &nbsp; If a picture is worth a thousand words, then here's..... well, a few thousand words for you.</span></div><br /><div style="text-align: justify;"><span style="font-size: large;">The cobbled stuff you see on that perf board is a single-ended to differential signal converter. It sounds fancy, but it's just 2 amps in an inverting and non-inverting configuration. This is to test the TPA6120 op-amp to see if everything got soldered on properly.</span><br /><span style="font-size: large;"><br /></span><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-_rGt8THQXYg/WXDWCr3cyII/AAAAAAAADXg/DgMp60EiPm8dTY4sbZcMCYUV3EE_VFSrQCKgBGAs/s1600/19727260_1322024984577431_77346898_o.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="180" src="https://1.bp.blogspot.com/-_rGt8THQXYg/WXDWCr3cyII/AAAAAAAADXg/DgMp60EiPm8dTY4sbZcMCYUV3EE_VFSrQCKgBGAs/s320/19727260_1322024984577431_77346898_o.jpg" width="320" /></a></div><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-S4ncC9lGLxU/WWkhrslOHnI/AAAAAAAADUY/gDRODMw-L5gtAs4XY51kMGgJhL1y-BH-ACKgBGAs/s1600/LT_Spice%2BSingle%2Bto%2Bdiff.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="790" data-original-width="1600" height="196" src="https://2.bp.blogspot.com/-S4ncC9lGLxU/WWkhrslOHnI/AAAAAAAADUY/gDRODMw-L5gtAs4XY51kMGgJhL1y-BH-ACKgBGAs/s400/LT_Spice%2BSingle%2Bto%2Bdiff.jpg" width="400" /></a></div><br /><br /><div style="text-align: justify;"><span style="font-size: large;"><span style="font-size: medium;"></span><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; In the scope pics, the yellow trace is the input signal (before the differential converter) and the blue and pink (or magenta? hell if I know) are the outputs of the TPA. The dark blue trace (the lowest trace) is the output of the op-amp. One channel only.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-gFvL1ssGkdc/WWHljfN8EVI/AAAAAAAADMw/SYA8GldA8kcpLIANZoX_VYa5qHXuYea6gCKgBGAs/s1600/19748003_1322024877910775_181754497_o.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="180" src="https://3.bp.blogspot.com/-gFvL1ssGkdc/WWHljfN8EVI/AAAAAAAADMw/SYA8GldA8kcpLIANZoX_VYa5qHXuYea6gCKgBGAs/s320/19748003_1322024877910775_181754497_o.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-frZXfVOageQ/WWHljaDMZ_I/AAAAAAAADMw/-nDarbNNYnIOhMjhVY9zIJGwpowt3k-BgCKgBGAs/s1600/19718680_1322024964577433_1608089758_o.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="180" src="https://1.bp.blogspot.com/-frZXfVOageQ/WWHljaDMZ_I/AAAAAAAADMw/-nDarbNNYnIOhMjhVY9zIJGwpowt3k-BgCKgBGAs/s320/19718680_1322024964577433_1608089758_o.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-6gZxKf9pprw/WWHljQckETI/AAAAAAAADMw/rPAsrhJrhxkf0B4fJADRhDCNvQP6O1zBgCKgBGAs/s1600/19686617_1322024884577441_1148145644_o.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="180" src="https://3.bp.blogspot.com/-6gZxKf9pprw/WWHljQckETI/AAAAAAAADMw/rPAsrhJrhxkf0B4fJADRhDCNvQP6O1zBgCKgBGAs/s320/19686617_1322024884577441_1148145644_o.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-MDhdNpxdQpo/WWHljQ8trnI/AAAAAAAADMw/KkPSjroq-vI3FTlEAb9FsI7iLxyvZYW1wCKgBGAs/s1600/IMAG3672.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://2.bp.blogspot.com/-MDhdNpxdQpo/WWHljQ8trnI/AAAAAAAADMw/KkPSjroq-vI3FTlEAb9FsI7iLxyvZYW1wCKgBGAs/s320/IMAG3672.jpg" width="320" /></a></div><br /><div style="text-align: justify;"><span style="font-size: large;">You might recognize the beast that is the &nbsp;<a href="http://electronicsplayground.blogspot.ro/2017/01/interstate-electronics-corporation-spg.html">Interstate Electronics generator</a> in the pics. I'm happy to say that it's running quite nice for its age. It has the occasional hiccup at power-on, but nothing a little hard rest can't cure.</span></div><div style="text-align: justify;"><br /></div><span style="font-size: x-large;"><b>Tying up loose ends</b></span><br /><span style="font-size: x-large;"><b><br /></b></span><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-tt7-dlajkUg/WWNcp5fxdeI/AAAAAAAADNQ/Nc0jAXiLdfUrz48XJEp501C9KL5ZGG3ZwCKgBGAs/s1600/IMAG3742.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://1.bp.blogspot.com/-tt7-dlajkUg/WWNcp5fxdeI/AAAAAAAADNQ/Nc0jAXiLdfUrz48XJEp501C9KL5ZGG3ZwCKgBGAs/s320/IMAG3742.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KQIp4auMyXg/WWNcp7kd_UI/AAAAAAAADNQ/MPLcMhFjjRc5U3BQNV7AZWXwdGs620dEQCKgBGAs/s1600/IMAG3743.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1067" data-original-width="1600" height="213" src="https://1.bp.blogspot.com/-KQIp4auMyXg/WWNcp7kd_UI/AAAAAAAADNQ/MPLcMhFjjRc5U3BQNV7AZWXwdGs620dEQCKgBGAs/s320/IMAG3743.jpg" width="320" /></a></div><br /><div style="text-align: justify;">&nbsp; <span style="font-size: large;">&nbsp; I stuck a heatsink onto the TPA6120 op-amp because during my tests with an open case showed that the op-amp will heat up to 55 degrees C and stabilize at this point. I figured that once it'll be put in its enclosure, together with all the other heat sources, it might get a little too toasty for long term reliability, therefore, I give you the pic above.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; The grey square is a silicone pad. Even though the heatsink is anodized aluminiun, I just wanted to make sure it'll never touch the resistors next to the amp. I've laso added heatsinks to the Pi's chips as well. Those are underneath the DAC hat.</span></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-M2C5T-spdAI/WW97kSvUK7I/AAAAAAAADVw/5B0BdNMWxUwlGPTFSH5XxVmmv55CiM7RQCKgBGAs/s1600/20170708_172714.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://4.bp.blogspot.com/-M2C5T-spdAI/WW97kSvUK7I/AAAAAAAADVw/5B0BdNMWxUwlGPTFSH5XxVmmv55CiM7RQCKgBGAs/s320/20170708_172714.jpg" width="320" /></a></div><br /><br /><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Being &nbsp;the paranoid guy that I am, even though the PSUs are mounted on 3.5mm nylon standoffs, I thought I'd play it extra safe and add some isolation between the case and the through-hole pins carrying live mains.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Another important thing would be the DAC output filter. &nbsp;The data sheet for the PCM mentioned using 1nF NP0/C0G caps. &nbsp;Now, I'm no audio guru, but &nbsp;an electric guitar mostly sounded as if it wanted to come at you and cut off you ears with a bread knife. The 3dB point of the filter with the original 1nF caps was 422 KHz, so I changed these to 2.2nF caps, decreasing the bandwidth to ~300 kHz.</span><br /><span style="font-size: large;">&nbsp; This is what LTSpice told me, so that's what I'm tellng you now.</span><br /><span style="font-size: large;">&nbsp; &nbsp; It made for a much cleaner sounding audio experience, especially on the highs. The issue was most likely caused by intermodullation products making thair way into the audio range. By reducing the filter's bandwidth, some of the haronics were attenuated, rendering a nicer, cleaner sound.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; I might consider going all the way up to 3.3nF caps just to see what happens....</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;Oscillators, anyone? get your free oscillators here!!</span></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-GmuCWpGsF0Q/WWfRhKeC8QI/AAAAAAAADTc/P_SEOMneDBUhuevL3FatTkjViLDTdcOeQCKgBGAs/s1600/1n%2B3db%2Bpoint.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="225" src="https://2.bp.blogspot.com/-GmuCWpGsF0Q/WWfRhKeC8QI/AAAAAAAADTc/P_SEOMneDBUhuevL3FatTkjViLDTdcOeQCKgBGAs/s400/1n%2B3db%2Bpoint.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-dNEJEJpvCXg/WWfRhMFH1rI/AAAAAAAADTc/No0p4gQna4Uhu0MqY0aGGQOfxky3Nxd9wCKgBGAs/s1600/2n2%2B3db%2Bpoint.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="225" src="https://3.bp.blogspot.com/-dNEJEJpvCXg/WWfRhMFH1rI/AAAAAAAADTc/No0p4gQna4Uhu0MqY0aGGQOfxky3Nxd9wCKgBGAs/s400/2n2%2B3db%2Bpoint.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-wt-T_FCLy_k/WWfRhPBt4-I/AAAAAAAADTc/CJqk5GHBmCsXROafIn0BJgA5oyrbxp7egCKgBGAs/s1600/3n%2B3db%2Bpoint.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1600" height="225" src="https://4.bp.blogspot.com/-wt-T_FCLy_k/WWfRhPBt4-I/AAAAAAAADTc/CJqk5GHBmCsXROafIn0BJgA5oyrbxp7egCKgBGAs/s400/3n%2B3db%2Bpoint.jpg" width="400" /></a></div><br /><br /><br /><b style="font-size: x-large;"><span style="font-size: x-large;">Performance</span></b><br /><br /><div style="text-align: justify;">&nbsp;<span style="font-size: large;"> &nbsp; Well, if youre wondering about geeky stuff like THD and noise performance, you're not the only one. I lack the proper equipment, but I do plan to build me some &nbsp;nice THD measurement unit.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Quoting the THD figures from the DAC's datasheet isn't that relevant, but might I remind you that the supplies for the DAC and op-amp are linear ones and the DAC's channel outputs are differential, so the only significant part, susceptible to noise pick-up is the op-amp itself. But because it has a high PSRR and the ground loops are (I think) on the &nbsp;small side, there is a fair chance that the distiortions on the audio output of the hat might be quite low.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Untill I find the equipment to make real world measurements, I can only say that to my ears, the DAC hat is a success. A 196 KHz, 24 bit &nbsp;song sounds prety impressive, so for now, this is where things stand</span></div><br /><b><span style="font-size: x-large;">Volumio Set-up</span></b><br /><br /><div style="text-align: justify;">&nbsp; &nbsp;<span style="font-size: large;"> Well, there are lots of places online detailing how to get your Volumio up and running. So why not add another one the list?</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; OK, so it's pretty easy. Just go to the Volumio download page and get the latest build. That will be in a .zip format and inside that there will be a .iso file.</span></div><div style="text-align: justify;"><span style="font-size: large;">After you've formatted you SD card &nbsp;(I formatted mine as a FAT32) you plug it in and write the image to the card.</span></div><div style="text-align: justify;"><span style="font-size: large;">Hold on, it's coming.... For writing the image file, I used Win32 Disk Imager. It's basically "point and shoot", so there's no reason to go into further details.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">....and here comes the fun part. Once you write your .iso file &nbsp;(not the .zip, like I did...doh!) just plug the card into your Raspberry and you're on your way.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Of course, once it boots up, you have to access it. I only access mine over LAN, so I don't know much about the wireless set-up, but I can assure you that once it's all booted up, you can go and write in your browser&nbsp;<b><a href="http://volumio.local/playback">http://volumio.local/playback</a>&nbsp;</b>and you should be in like Flynn...</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; On the off chance this doesn't work, you'll have to go into your router and see what devices are connected to it. The DAC should come up as "Volumio". Then just access it via its IP address.</span></div><br />&nbsp; <br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-23LmIsn2iJo/WW-Bc__o3sI/AAAAAAAADWI/q0tYqBHgEWkr9PV1RySD0Q_tNHG_bbkOQCKgBGAs/s1600/Volumio%2BNetwork%2BShare%2BSetting.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="793" data-original-width="1600" height="197" src="https://2.bp.blogspot.com/-23LmIsn2iJo/WW-Bc__o3sI/AAAAAAAADWI/q0tYqBHgEWkr9PV1RySD0Q_tNHG_bbkOQCKgBGAs/s400/Volumio%2BNetwork%2BShare%2BSetting.jpg" width="400" /></a></div><br /><br /><div style="text-align: justify;">&nbsp; <span style="font-size: large;">&nbsp; Let's say you want to share the folder "Music</span><span style="font-size: large;">".</span><br /><span style="font-size: large;">&nbsp; If you have a NAS, just type in its IP address and the name of the file you want Volumio to play from. Do not leave the "Alias" field blank. You have to write something there or the sharing won't work. And, whaterver you do, please DO NOT share files with spaces in its name (e.g. My Music). It screws up the sharing somehow. I wasted an entire day with this crap. Just use underscores (e.g. My_Music) It'll save a lot of freakin' time.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; If you are just running a version of Linux on your NAS, select "nfs" from "File Share Type". However, if you're running Samba, then just leave the default "cifs"</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Ok, so you're no that fancy and &nbsp;just have a PC. No problem.... just do the same procedure as mentioned and leave the default "cifs" in the "File Share Type". If by any chance you have a user and password for you PC, then just write these in the appropriate fields. But really, who does that? Who has a passworded PC at home? That's no security, that's just a waste of time. You want security? &nbsp;Then run Linux on your PC. Everyone in the house will hate you.</span></div><div style="text-align: justify;"><br /></div><b><span style="font-size: x-large;">Final thoughts</span></b><br /><br /><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; I ended up building two almost identical DACs, one for me and one for a friend of mine. The only difference is that while I used a Raspbeery Pi 2 B+, his was a Raspberry Pi 3.</span></div><div style="text-align: justify;"><span style="font-size: large;">Our choice of web players was Volumio, which worked on both versions without a hitch. </span></div><div style="text-align: justify;"><span style="font-size: large;">Also, because the Pi 3 has built-in Wi-Fi, I added an antenna for it in the back of the case. If you need some more info about how to do this, you can check out <a href="https://hackaday.io/project/10091-raspberry-pi-3-external-antenna">this article</a>. It has a lot of nice pictures regarding this mod. Also, if you're going to do this, u.FL connectors are a pain to solder, so if I were to do it all again, I'd go with just soldering a coax cable to the Pi's PCB and tack it in place.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Like always, you can see the whole album of this build <a href="https://photos.app.goo.gl/FXI3sc3poFXw4tCO2">here</a>. Hope you like what you see and if you want to comment, leave one below. </span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Later edit: &nbsp;The DAC has been so far running non-stop for about a week and everything looks OK. The op-amp did start heating up as soon as I gave it power, so that heatsink really helps. I want to do a thermal profile of the DAC to see how it behaves in the long term, therefore I'm searching for a way to do some temperature data logging. I'll &nbsp;probably do a post on this as well, in the future,</span></div><div style="text-align: justify;"><br /></div><br /><br /><br /><br /><br /><br /><br />Disclaimer: The stuff from TI I bought myself. I'm in no way affiliated with them. It just happened that they have the kind of parts I &nbsp;needed<br /><br /><br /><br /><br />Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-10424562997939103682017-06-14T16:05:00.002+03:002017-07-15T19:12:53.533+03:00My Hi-Fi Raspberry Pi DAC project. The Design Phase<div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; I'm in no way an <strike>audiophool</strike>&nbsp;audiophile, but I do like to listen to good music coming from a nice bit of quality engineered speaker and amp.</span></div><div style="text-align: justify;"><span style="font-size: large;">I've had a Sony CD player ( CDP-X303 ES ) for a while now and while it's working nice, it has a huge drawback.</span></div><div style="text-align: justify;"><span style="font-size: large;">I have to buy a truck load of CDs just so that I can listen to my favorite songs. I tend to have a variety of preferences, mostly based on my mood, that's why I tend to listen to anything from Michael Jackson to &nbsp;Linkin Park and from Run DMC to Eminem. And anything in between.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; &nbsp;It's much more convenient to <strike>download</strike>&nbsp;ahem.... BUY my favorite tracks and store them on a drive and listen to them from some kind of network DAC. It's also easy on the mind to know that if a track has some kind of artefacts in it, (Sone CDs I bought have these) you just delete it and <strike>downl</strike>.... buy another. Unlike CDs, where you just have to live with the thought that something you paid money on &nbsp;has random shitty, thunderous noises on it.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">PS: Don't buy the Michael Jackson CD albun "The Essential Michael Jackson" from Sony Music. You'll be trully regret it if you do. At least, I did.</span></div><br /><div style="text-align: justify;"><span style="font-size: large; font-weight: bold;"><br /></span></div><div style="text-align: justify;"><b style="font-size: x-large;"><span style="font-size: x-large;">A Networked DAC</span></b></div><br /><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp;<span style="font-size: large;"> So, first of all, I need a board that links whatever DAC I'll make, to my LAN at home, so I can access the songs. And &nbsp;it'd be nice to also play them.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;It'd be even better if I don't have to spin a whole board for this, so I'm thinking something along the lines of an Arduino or Raspberry Pi.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; I want to be able to play stuff like FLAC or WAV at something like 192 to 380 Kbps, 24 or 32 bits. Also, the few DACs that can handle these bit rates have an I2S (no, it's not a typo) interface, and conveniently enough, a few platforms have an I2S &nbsp;bus available.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; One such platform is the Raspberry Pi. It's &nbsp;cheap, has a ton of processing power and best of all, there are a lot of debians and ready-made software for it, covering almost anything you can think of.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Another option would be the Odroid., which also has enough umph for the task at hand.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; For those cringing at the sound of using platforms like these for Hi-Fi, please keep your composure. &nbsp;Your finely-tuned ears can't really tell the difference between a 1000 $ DAC and an embedded platform with a good DAC on it (except if the latter is poorly designed).&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Now, having said this, please excuse me while I go put on my flame suit.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; My decision went in favor of the Raspberry Pi platform just because I happened to have one around.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">A quick search for a Raspberry debian that can handle all you music via a network interface will produce the following results:</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- Volumio</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- Rune Audio</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- Etc.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; There are a lot of web players out there that do &nbsp;the same thing. My personal choice was Volumio. Why did I choose this over the others I hear you ask ? Well, because this was the first result that popped up on Google.</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: x-large;"><b>Which one... which..one... Hmm...</b></span></div><div style="text-align: justify;"><span style="font-size: large;"><b><br /></b></span></div><div style="text-align: justify;">&nbsp; &nbsp;<span style="font-size: large;"> So, having solved the networking part, now all I need is a DAC that can do everything I want i.e. up to 382 Kbps at 32 bits.</span></div><div style="text-align: justify;"><span style="font-size: large;">A friend of mine did a similar project and he used the <a href="http://www.ti.com/lit/ds/symlink/pcm5242.pdf">PCM5242</a> from Texas Instruments. It has a very impressive spec sheet, both in performance and in size. But the size is mostly due to its internal DSP. Yep, this DAC also has an &nbsp;mini DSP inside. Wicked! That opens up a whole new world of opportunities.</span></div><div style="text-align: justify;"><span style="font-size: x-large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: x-large;"><b>Where's the rest of it?</b></span></div><div style="text-align: justify;"><span style="font-size: large;"><b><br /></b></span></div><div style="text-align: justify;">&nbsp; &nbsp;<span style="font-size: large;"> Anyone looking at the datasheet for this can plainly see the banner on the front page, where it says it has &nbsp;a DSP inside it. But if you go on further, you start &nbsp;to see that the datasheet is incomplete. It's missing some of the data on the DSP registers. Bummer. Plus, if you want to program it via an interface, you need TI's Pure Path Studio software...which can not be downloaded from anywhere. You have to send the guys at TI a mail with a request for it.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Also, take note that there are a few commercial Raspberry shields out there that have the PCM5242. These claim it has a DSP inside &nbsp;it, which is correct. Unfortunately, if you want to use it or program it, or do anything with it, other than just convert bits to sound, you're on your own. You basically have to create your own library for the PCM's DSP so you configure every bit of it.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; But let's not let this small drawback keep us from implementing what would be a very capable DAC</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; I'm going to build one to see how it sounds and how it behaves and if I like it, I'm going to design another version where I try to use the internal DSP and actually put the whole thing to use.</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><b><span style="font-size: x-large;">Actually designing stuff</span></b></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; <span style="font-size: large;">&nbsp; Ok, so let's see how we're going to do this.</span></div><div style="text-align: justify;"><span style="font-size: large;">First thing's first: a normal I2S interface uses 4 wires.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- A master clock, to time the whole thing - MCLK or SCK;</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- A bit-rate clock, BCK, that tells the DAC what bitrate the song is being played at, i.e. you sampling frequency;</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- The data line, DIN</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;- &nbsp;And a signaling line &nbsp;- LRCK - to tell the DAC which frame of &nbsp;data is for the right channel and which is for the left one.</span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-WLlbnldSJXI/WWZV1uOUUWI/AAAAAAAADQQ/XNKEGQ2winkxMbqdRaFsMXIKdtN7bxvNACKgBGAs/s1600/I2S_Full.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="132" data-original-width="472" height="111" src="https://3.bp.blogspot.com/-WLlbnldSJXI/WWZV1uOUUWI/AAAAAAAADQQ/XNKEGQ2winkxMbqdRaFsMXIKdtN7bxvNACKgBGAs/s400/I2S_Full.jpg" width="400" /></a></div><div style="text-align: center;"><div style="text-align: center;"><br /></div><div style="text-align: center;">Fig.1 &nbsp;I2S Bus with all 4 signals.BCK is derived from the MCK</div></div><div style="text-align: center;"><div style="text-align: justify;"><br /></div></div><div style="text-align: center;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-ABGoWTkd7WI/WWZUJQdv1vI/AAAAAAAADP0/gp2W48yUjUszCTwJwlrkGq2dVp5_mQm0ACKgBGAs/s1600/I2S.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="128" data-original-width="462" height="110" src="https://1.bp.blogspot.com/-ABGoWTkd7WI/WWZUJQdv1vI/AAAAAAAADP0/gp2W48yUjUszCTwJwlrkGq2dVp5_mQm0ACKgBGAs/s400/I2S.jpg" width="400" /></a></div><div style="text-align: center;"><div style="text-align: center;"><br /></div><div style="text-align: center;">Fig.2 &nbsp;I2S Bus implementing only 3 signals. MCK is&nbsp;</div></div><div style="text-align: center;"><div style="text-align: center;">internally reconstructed from the BCK</div></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; <span style="font-size: large;">Normally, the master clock would have to be set so that it is a multiple of the BCK. This means that with most network &nbsp;DACs (I'm talking about the system as a whole, not the DAC chip itself) you need to have an external clock feeding the DAC directly, or an interface IC, (bridging something like USB - I2S) when an interface conversion is necessary. This is kind of cumbersome and adds a lot of parts to your BOM.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; If you are curious, you can have a look at XMOS's line-up of chips. There are some that go up to 192 k.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; But the PCM5242 only needs one clock - the BCK. It can take this and rebuild the master clock with an internal PLL, thus saving a lot of board space and simplifying the design.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;The 5242 can work either in Hardware mode, or Software mode.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;Hardware mode is kind of a stand-alone thing. You just feed it 1s and 0s from an I2S bus, then it converts them to sound. Easy. You also have some pins with which to control signal attenuation, and that's about it. I'm over-simplifying, but you get the point.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Software mode is where the magic really happens. You still use the I2S bus, but you can also do soft muting on the DAC, you can control the volume in much finer steps, set PLL frequencies, write internal registers and also, my favorite, control the DSP. All this through an I2C or SPI interface. Your choice. Or, rather my choice, to be exact.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; The prototype is going to just run in HW mode. I don't want to deal with writing any internal registers and doing power ON/OFF sequences and stuff like that. At least, not just yet. I just want to see it work....or to be more precise, to hear it work.</span></div><br /><div style="text-align: justify;"><span style="font-size: large; font-weight: bold;"><br /></span></div><div style="text-align: justify;"><b><span style="font-size: x-large;">Down to the nitty-gritty</span></b></div><br /><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; <span style="font-size: large;">Ok, so having settled on hooking the DAC so it works in Hardware Mode, what other egineering stuff do we need, to make this thing work?</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; My Sony amp has 1 Vpp inputs, but from what I've seen, it can tolerate higher peak-to-peak voltages. Up to 4 or 5 Vpp. I actually scoped a Sony 339ES CD player and got as much as 7Vpp.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;But for safety's sake, let's choose a maximum output voltage of 2 Vpp for the DAC hat.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; The DAC itself can output either 4.2 Vpp or 2.1 Vpp levels. So, let's go with the 2.1 Vpp.</span></div><div style="text-align: justify;"><span style="font-size: large;">Now, I'm kind of weary about powering the amp's input directly from the DAC, so &nbsp;I want to put a buffer between them.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;Because I'm lazy, &nbsp;and don't want to mess around with op-amps possibly oscillating like crazy, I'm going to go with the&nbsp;<a href="http://www.ti.com/lit/ds/symlink/tpa6120a2.pdf">TPA6120A2</a>&nbsp;audio amp as the buffer. That's the one in the DAC's data sheet.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Thus, the final output will have a level of about 4 Vpp (the amp's minimum gain is x2) but we can solve that with some extra attenuation from the DAC. For this, you just implement the table below so that your signal has the needed level.</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-tt3s5j1O3ro/WWZZ6tM7Y_I/AAAAAAAADQs/F6TMvtFJTJklAEI8VUDYbmsLWmNVnCVQACKgBGAs/s1600/PCM5242%2BTable.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="390" data-original-width="538" height="231" src="https://3.bp.blogspot.com/-tt3s5j1O3ro/WWZZ6tM7Y_I/AAAAAAAADQs/F6TMvtFJTJklAEI8VUDYbmsLWmNVnCVQACKgBGAs/s320/PCM5242%2BTable.jpg" width="320" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: x-large;"><br /></span></div><div style="text-align: justify;"><b><span style="font-size: x-large;">Analog and digital power supplies design</span></b></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;"><b>3.3V PSUs</b></span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; The DAC needs both an analog power supply and a digital one, both 3.3V. This isn't such a big deal. But I can sure as hell try and make one out of it.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; One can easily fit a small SMPS or two on a Pi hat. The problem is however the noise these will generate. Ok, this, and the fact that some audiophiles will cringe at hearing the words "SMPS" and "Hi-Fi" in the same sentence.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; I want everything to be as clean as possible, noise wise, so my solution was to split the power supply from the main DAC board. Not only that, I went a step further and split the analog and digital supply, each having its own board.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Having this configuration however can be more detrimental than helpful. One might be tempted to think that a current's return path would be that of least resistance to ground. And that is correct.. But where that ground is, that can be a bit tricky to find.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; In the set-up I proposed, the ground is not the one on the DAC hat i.e. the PCM's GND connections. It's the one way over on the PSU. So, the actual path would be DAC → about 5 cm of wires (2 inches for the non-MKS lovers) → PSU GND</span></div><div style="text-align: justify;"><span style="font-size: large;">With such a large loop area, &nbsp;it's an open invitation to a whole lot of noise pick up, no matter how quiet the actual PSU is.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;I tried to mitigate this by having the PSUs regulate down to 5V for the PCM's power rails then have an additional LDO on the Pi hat itself, to do the rest of the work down to 3.3V. This &nbsp;(I'm hoping) will "bring back" the GND return path to the hat. The current loop this set-up creates is the shortest possible.</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;"><b>To split o not to split, that is the question</b></span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;A recurring issue in this Analog-meets-Digital world appears: how to manage the digital and &nbsp;analog ground planes for the DAC?</span></div><div style="text-align: justify;"><span style="font-size: large;">Having both an analog and a digital rail, how exactly do you route the grounds on the board so that you get the lowest possible EMI and the least amount of noise pick-up on you signal lines? Do you split them clear through the middle and place the DAC right on the center line? Or do yo just make on continuous plane?</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; There are lots of articles &nbsp;dealing with this exact issue, and depending on when it was written, you might get some diverging answers.</span></div><div style="text-align: justify;"><span style="font-size: large;">I have come across a couple of articles that explain the issue very well.</span></div><div style="text-align: justify;"><span style="font-size: large;">One is <a href="http://www.hottconsultants.com/techtips/split-gnd-plane.html">this</a>&nbsp;article, which kind of gets you on the right path. If you need to go deeper down the rabbit hole, I recommend reading "Grounding in mixed-signal systems demystified", parts <a href="http://www.ti.com/lit/an/slyt499/slyt499.pdf">1</a> and <a href="http://www.ti.com/lit/an/slyt512/slyt512.pdf">2</a>, from Texas Instruments.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Following the general direction from these articles, I decided to only join my grounds under (or close to) the PCM DAC and exercise the right routing technique so that I have no analog signal wires crossing the digital ground or vice versa.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Now, for this design, it's pretty easy to get things right, it's only going to be a two layer board and there are only 4 ICs and some passives on it, but for other designs, it can get messy when routing signal lines across the PCB, and keeping &nbsp;the traces in their right ground plane can cause you some head aches</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: x-large;"><b>Cap selection</b></span></div><br /><div style="text-align: justify;"><span style="font-size: large; font-weight: bold;"><br /></span></div><div style="text-align: justify;">&nbsp;<span style="font-size: large;"> No, I don't mean electrolytics. That's a discussion for another time. &nbsp;I mean SMD ceramic caps. As in MLCC caps.</span></div><span style="font-size: large;"><br /></span><br /><div style="text-align: justify;"><span style="font-size: large;">In this design, there are a few places where caps really matter, despite being used mostly for bypassing.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; The 3.3V regulators on the DAC board are LP2992 LDOs. Yes, Texas Instruments again. Now, these are advertised as having very low noise, and to achieve this, the datasheet recommends using some very low ESR caps on the input and output &nbsp;and NP0 or C0G caps on the Bypass pin.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;My personal choice was to go with X7R caps for the 5V input and 3.3V output caps. The rest of the bulk capacitance will be on the PSU boards.</span><br /><span style="font-size: large;">These have much lower ESR than electrolytics and behave much better under DC bias than X5R caps. Tantalums are on my naughty list and try to avoid them as much as possible. They don't take voltage spikes that well and their ESR isn't really that low.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; Also, the X7R material is less sensitive to changes in capacitance due to temperature and/or DC voltage (compared to X5R, that is).</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; NP0 and C0G dielectrics are literally in a higher class than X7R / X5R. While one might use the latter in normal bypassing applications, the NP0/C0G can be used in filters, or for setting precise time constants. If you were to plot a frequency vs capacitance chart, you'd get pretty much a straight line from DC to about 10 MHz and a somewhat linear temperature coefficient.</span></div><div style="text-align: justify;"><span style="font-size: large;">This makes them very useful for, say.... some nice RC filters that go on the output of a DAC. And it just so happens that we have some of these between the DAC's differential output and the op-amp's input.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; You can find a lot of info about this on the net, so I won't bore you with too many details. You can check out <a href="http://www.koaspeer.com/pdfs/TN-196R14NPO-Y5V.pdf">this</a> document I found in haste, while deciding which type of cap I should use. It's got graphs and tables in it , so it must be good.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><b><span style="font-size: x-large;">Hardware Mode configuration pins</span></b></div><br /><div style="text-align: justify;"><span style="font-weight: bold;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Like I mentioned earlier, the PCM5242 can be used in Hardware Mode or in Software Mode, making it a very flexible design.</span></div><span style="font-size: large;"><br /></span><br /><div style="text-align: justify;"><span style="font-size: large;">&nbsp; First off, to put the DAC in Hardware mode, pins <b>24</b> and <b>23 </b>need to be pulled low.</span></div><div style="text-align: justify;"><span style="font-size: large;">Now, there aren't many control options left. You can choose between a 2V<span style="font-size: xx-small;">RMS</span> output or a 1V<span style="font-size: xx-small;">RMS</span> output by making pin <b>21 </b>Low or High, respectively (i.e. 1V out for AGNS high).</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; I've already talked about the attenuation output pins so that's the important bits taken care of.</span></div><div style="text-align: justify;"><span style="font-size: large;">What's left is to set pin <b>16 </b>Low, because we don't want any de-emphasis, and if you don't want to hear any hissing in your speakers when nothing's playing, then you'd want to set pin <b>1 </b>Low.</span></div><div style="text-align: justify;"><span style="font-size: large;">There, that about covers it.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><b><span style="font-size: x-large;">Schematic and PCB Layout</span></b></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; If you're interested in building something similar or just want to have a look over the schematic, you can go to my <a href="https://github.com/catt87/Raspberry-DAC-Files">GitHub</a> &nbsp;project page. There I have all the documents relating to this project. Feel free to download and/or use the desing as you might see fit.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; The laying out of the PCB went pretty much as I'd expect it for this simple design. Like I wrote, I opted to do the joined AGND and DGND sollution.</span></div><div style="text-align: justify;"><span style="font-size: large;">Unfortunately, because I wanted the bypass caps for the DAC as close to the pins as possible, I didn't have ena clear way to split the ground right beneath the DAC, so they're joined in two locations, either side of the DAC</span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-5GHpArodCX4/WWewhbUnSDI/AAAAAAAADRc/aX940cLwrgct_IWQofTWzt67BwLjF-o3ACKgBGAs/s1600/DAC%2BGND.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="737" data-original-width="1069" height="275" src="https://4.bp.blogspot.com/-5GHpArodCX4/WWewhbUnSDI/AAAAAAAADRc/aX940cLwrgct_IWQofTWzt67BwLjF-o3ACKgBGAs/s400/DAC%2BGND.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; <span style="font-size: large;">&nbsp;This may look weird, but I don't think it impacts the noise performance of this thing too much. But, if you believe otherwise and have more experience than me, then please leave a comment below, I'd really like to hear some nice explanations.</span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-zfnjD41E8OY/WWezctOkyuI/AAAAAAAADSA/QgVeO6sO3qQrSZSxJ9CzAfpO8xRHB9M1gCKgBGAs/s1600/DAC%2B3D%2BPCB.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="859" data-original-width="1055" height="325" src="https://1.bp.blogspot.com/-zfnjD41E8OY/WWezctOkyuI/AAAAAAAADSA/QgVeO6sO3qQrSZSxJ9CzAfpO8xRHB9M1gCKgBGAs/s400/DAC%2B3D%2BPCB.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp;<span style="font-size: large;"> &nbsp; So, basically, this is what I'm expecting to get from the PCB manufacturer. Except in black. It's going to be gorgeous.</span></div><div style="text-align: justify;"><span style="font-size: large;">Oh, and for those of you wondering what those holes on the bottom of the picture are.... wel,, I figured I'll just solder the audio output cable straight to the PCB. And to firmly hold the cable there and not put pressure on the solder joints, I figured I'd zip tie the cable to the PCB. A bit flakey? Maybe. But I &nbsp;didn't want too many metal to metal interface between the output of the DAC and the input of my speaker amp. I may&nbsp;</span><span style="font-size: large;">possibly</span><span style="font-size: large;">&nbsp;be dellusional here, but hey... I like to experiment.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; The PSU layout also went snoothly and looking back, I could have squeezed both PSUs onto a single board or two smaller boards than the ones that came out. Next time I'll know better.</span></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-TJeHB-i9I60/WWe26NwjB9I/AAAAAAAADSs/ODY3t4XzOC0aTtXKth19R-Z5zcbRAc7ZgCKgBGAs/s1600/Analog%2BPSU%2B3D.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="829" height="391" src="https://3.bp.blogspot.com/-TJeHB-i9I60/WWe26NwjB9I/AAAAAAAADSs/ODY3t4XzOC0aTtXKth19R-Z5zcbRAc7ZgCKgBGAs/s400/Analog%2BPSU%2B3D.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-mkmdQLHZv3M/WWe26JGro0I/AAAAAAAADSs/nk3zj2FiVYUHheLj35NfClP3uGkhve4LQCKgBGAs/s1600/Digital%2BPSU%2B3D.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="781" data-original-width="777" height="400" src="https://3.bp.blogspot.com/-mkmdQLHZv3M/WWe26JGro0I/AAAAAAAADSs/nk3zj2FiVYUHheLj35NfClP3uGkhve4LQCKgBGAs/s400/Digital%2BPSU%2B3D.jpg" width="397" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; <span style="font-size: large;">&nbsp; Now, all that's left is to wait for the boards and parts to arrive.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; If you would like &nbsp;to read on about how I put everything together, tested this and how it all turned out, the second part of this build is here.</span><br /><span style="font-size: large;"><br /></span><br /><div style="text-align: start;">Disclaimer: The stuff from TI I bought myself. I'm in no way affiliated with them. It just happened that they have the kind of parts I &nbsp;needed</div><div><br /></div></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-81411101864185687902017-04-04T17:41:00.001+03:002017-04-04T18:09:37.572+03:00Transformer Coil Winding Jig&nbsp; &nbsp; <br /><div style="text-align: justify;">&nbsp; &nbsp; &nbsp;If you can do it, then why not over-do it. At least that's what I did with this project. It started out small....just a simple motor, stick a bobbin on the end of it then wind away to you heart's content....Naaaa!</div><div style="text-align: justify;"><br /></div><span style="font-size: large;"><b>I need to control this...</b></span><br /><br /><div style="text-align: justify;">Indeed, I do. And since &nbsp;this will be a "hand winding" operation, it implies that both hands will be preoccupied with the....well, winding, of course. Therefore, who's going to control the motor?&nbsp;</div><div style="text-align: justify;">And since humans happen to have four limbs, an obvious candidate to fill in the position would be - a foot...by means of a pedal. Ergo, I need to make myself a foot pedal to properly control the motor. And not just an ON/OFF kind of control. No no no....I want speed control.</div><br /><br /><b><span style="font-size: large;">Choices... so many choices....</span></b><br /><b><span style="font-size: large;"><br /></span></b><br /><div style="text-align: justify;">&nbsp; &nbsp; Ok, so how about the heart of this thing? The motor. What kind of motor should I use? Well, a DC motor from an electric drill would have been enough. But like I said, why not overdo it. So, I had a Stepper motor driver available. It's an&nbsp;<span style="background-color: white; color: #333333; font-family: &quot;arial&quot; , sans-serif;"><a href="https://www.pololu.com/product/2970" target="_blank">AMIS-30543</a>&nbsp;</span><span style="background-color: white; color: #333333;"><span style="font-family: inherit;">stepper motor driver that can do up to 3A per coil. Works for me.</span></span></div><span style="background-color: white; color: #333333;"><span style="font-family: inherit;"><br /></span></span><br /><div style="text-align: justify;"><span style="background-color: white; color: #333333;"><span style="font-family: inherit;">&nbsp; &nbsp;Now what kind of stepper? Some might think, "a NEMA17 stepper would do it". Not!&nbsp;</span></span></div><div style="text-align: justify;"><span style="color: #333333;"><span style="background-color: white;">From my pile of steppers, of course I went ans picked the biggest &nbsp;most powerful stepper I had. It's a NEMA23, 3Nm &nbsp;stepper motor. You might think it's overkill. But Since I do a lot of SMPS and high power stuff, there will come a time when some 0.7mm or 1mm magnet wire will have to be wound. And that requires a lot of torque at low speed. Yes, an electric drill ca provide that. I know, I know. I just don't want to use that.</span></span></div><div style="text-align: justify;"><span style="color: #333333;"><span style="background-color: white;"><br /></span></span></div><span style="color: #333333;"><span style="background-color: white;"><br /></span></span><span style="color: #333333; font-size: large;"><span style="background-color: white;"><b>Strange things are afoot</b></span></span><br /><span style="color: #333333; font-size: large;"><span style="background-color: white;"><b><br /></b></span></span><br /><div style="text-align: justify;"><span style="color: #333333;"><span style="background-color: white;">&nbsp; &nbsp; Now for the control part - The pedal.</span></span></div><div style="text-align: justify;">I initially though I could do the pedal with springs... big powerful springs. Of course, that didn't really pan out. The spring itself was OK, but the wire setup would either get snagged or the wire (guitar string wire) would stretch out and &nbsp;wouldn't tension the spring properly.</div><div style="text-align: justify;">&nbsp; &nbsp; But, being the engineer that I am, I often get inspiration from things around me. This time, it was a cupboard door hinge that used a telescope to help raise and lower the door. BINGO!</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">I went to the hardware store, bought two of those furniture telescope things, came home, threw away the spring and wire and mounted the new mechanism. And it worked. Brilliantly, I might add. It feels just right. The pressure i have to put on the piston feels just about right. And it's very smooth and controllable.</div><div style="text-align: justify;"><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fNZFZyDE6PE/WOOm42C50YI/AAAAAAAADBE/FKSCSqbBAlAnpjgcysm4kjk8KG7pzXrYQCPcB/s1600/IMAG3503.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-fNZFZyDE6PE/WOOm42C50YI/AAAAAAAADBE/FKSCSqbBAlAnpjgcysm4kjk8KG7pzXrYQCPcB/s320/IMAG3503.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-Kp08MeimBIs/WOOm42dxLjI/AAAAAAAADBE/ZbP7Wi5AD4o1cdbT-1IqbGEzQxBsTvanACPcB/s1600/IMAG3504.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-Kp08MeimBIs/WOOm42dxLjI/AAAAAAAADBE/ZbP7Wi5AD4o1cdbT-1IqbGEzQxBsTvanACPcB/s320/IMAG3504.jpg" width="213" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bbQqK6JMYEE/WOOm464ycdI/AAAAAAAADBE/MS-Cn5pVHoMsQpJqB9ktQ4la8wJDGkQGQCPcB/s1600/IMAG3505.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-bbQqK6JMYEE/WOOm464ycdI/AAAAAAAADBE/MS-Cn5pVHoMsQpJqB9ktQ4la8wJDGkQGQCPcB/s320/IMAG3505.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-FG3E-5T15qQ/WOOm45alkaI/AAAAAAAADBE/-ZT_cOExOCsKuIYmchIBhKp-8-pEiv2mgCPcB/s1600/IMAG3506.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-FG3E-5T15qQ/WOOm45alkaI/AAAAAAAADBE/-ZT_cOExOCsKuIYmchIBhKp-8-pEiv2mgCPcB/s320/IMAG3506.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-3HpciWjhm50/WOOm42V5xYI/AAAAAAAADBE/yMkcqoT4Phw3sT2hmDFdUtKYl-ULmq28wCPcB/s1600/IMAG3507.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://4.bp.blogspot.com/-3HpciWjhm50/WOOm42V5xYI/AAAAAAAADBE/yMkcqoT4Phw3sT2hmDFdUtKYl-ULmq28wCPcB/s320/IMAG3507.jpg" width="213" /></a></div><br />The two nuts sticking out &nbsp;in the middle of the pedal will eventually get replaced by countersunk screw...eventually.<br /><br />The base is made out of &nbsp;15mm (590 thou, for those that still refuse to get with the program) thick resin impregnated fibres (cotton fibres, I think). Atop of that is a square polycarbonate piece, that holds the hinge. The pedal itself is made out of some kind of &nbsp;5mm thick fibre-glass resin material.<br /><br />If you're wondering about the routed edges and other stiff going on on the bottom black piece, well, don't They were already there. (I'm not that lucky as to posess a milling machine....yet)<br /><br />Now, I mentioned earlyer that I also want to have speed control.<br />That is done with a regular 10K potentiometer and a rack and pinion set.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-77Z1aQD7L4I/WOOm4xX6GwI/AAAAAAAADBM/Ae_lw9aaUHk75olY7nNMm13jFqZjne8LwCPcB/s1600/IMAG3508.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-77Z1aQD7L4I/WOOm4xX6GwI/AAAAAAAADBM/Ae_lw9aaUHk75olY7nNMm13jFqZjne8LwCPcB/s320/IMAG3508.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-6KW2DUWwUxs/WOOm40ytABI/AAAAAAAADBM/a7B0btSVmL03RP8f4vwgCT5iVNyTjSgmACPcB/s1600/IMAG3509.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-6KW2DUWwUxs/WOOm40ytABI/AAAAAAAADBM/a7B0btSVmL03RP8f4vwgCT5iVNyTjSgmACPcB/s320/IMAG3509.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-yIK5Ts9Byb8/WOOm418cGLI/AAAAAAAADBM/sqwbHNUPrqc3JcmvCXQa8ISjx5VEei0HgCPcB/s1600/IMAG3556.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-yIK5Ts9Byb8/WOOm418cGLI/AAAAAAAADBM/sqwbHNUPrqc3JcmvCXQa8ISjx5VEei0HgCPcB/s320/IMAG3556.jpg" width="320" /></a></div><br /><br />The parts were designed and printed by yours truly. Ok, only designed.. my 3D printer took care of the actual printing part.<br />&nbsp;The travel of the pedal actually matches to the 3-quarter-turns of the potentiometer. If you want to know how I did that....luck. Pure, dumb luck.<br />I thought I'd have to do some iterations before I got things to properly mesh (radius of the rack, number of teeth, pedal travel) but somehow I got it all in one go....<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-4oofmRZtMp8/WOO26Wj6KvI/AAAAAAAADB0/xso2eImj9aIehCUx6xv0fYkEp0vN8HUdgCPcB/s1600/IMAG3625.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-4oofmRZtMp8/WOO26Wj6KvI/AAAAAAAADB0/xso2eImj9aIehCUx6xv0fYkEp0vN8HUdgCPcB/s320/IMAG3625.jpg" width="320" /></a></div><br />Or maybe not...<br /><br /><br /><br /></div><div style="text-align: justify;"><span style="font-size: large;"><b>Keeping count of things</b></span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">120...121...122...130... Obviously, it's not an improvement to hand winding if there isn't a way to keep track of your turns.</div><div style="text-align: justify;">That shouldn't be too hard. The whole jig is already controlled by an Arduino, and it still has a lot of free pins. So let's use them.</div><div style="text-align: justify;">&nbsp; &nbsp;And since the motor happens to have an extended shaft out the back side, why not stick an infrared light barrier and a small wheel with a slot in it, on the shaft?<br />&nbsp;When the motor makes a full turn, it lets some light pass, the Arduino increments a counter on a display....Perfect!<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-LLqUp3no5Ow/WOOuoFW5hJI/AAAAAAAADBk/tGEeZ-es7PUeemfi4Gjvoytr6pZyKT0_ACPcB/s1600/IMAG3622.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-LLqUp3no5Ow/WOOuoFW5hJI/AAAAAAAADBk/tGEeZ-es7PUeemfi4Gjvoytr6pZyKT0_ACPcB/s320/IMAG3622.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-CpWDYAB3pzg/WOOuoDd4CuI/AAAAAAAADBk/ZS0kXNkLzNQ3t_M9v6EwzomumGv5PawYwCPcB/s1600/IMAG3623.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-CpWDYAB3pzg/WOOuoDd4CuI/AAAAAAAADBk/ZS0kXNkLzNQ3t_M9v6EwzomumGv5PawYwCPcB/s320/IMAG3623.jpg" width="320" /></a></div><br />The wheel was 3D printed and you can find the STL and Solidworks files for it right <a href="https://github.com/catt87/Coil-Winder">here</a>.<br /><br /><br /><br /><b><span style="font-size: large;">Putting all of it together</span></b><br /><br />I had to build some kind of stand, for the motor. Once again I used some 15mm black resin impregnated fibre material &nbsp;and some 15mm thick polycarbonate scraps that I had.<br /><br />The stepper was bolted to the frame with M4 screws.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-DT7UVsGD7G4/WOOm44YZgbI/AAAAAAAADBE/0F81BnJoQs8ajXP_gbjKl4f8awuvtsz6QCPcB/s1600/IMAG3478.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-DT7UVsGD7G4/WOOm44YZgbI/AAAAAAAADBE/0F81BnJoQs8ajXP_gbjKl4f8awuvtsz6QCPcB/s320/IMAG3478.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-P3m8oE9hBuU/WOOm4x8iBlI/AAAAAAAADBE/-TajbZ0H1akI9OwLaPzdFEPb0badqQbfgCPcB/s1600/IMAG3479.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-P3m8oE9hBuU/WOOm4x8iBlI/AAAAAAAADBE/-TajbZ0H1akI9OwLaPzdFEPb0badqQbfgCPcB/s320/IMAG3479.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-bm5cO2t1uDc/WOOm4ylR5LI/AAAAAAAADBE/2Ms5D6uZCfg8Ci4OMgkNgvvioQiHMkfXwCPcB/s1600/IMAG3480.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-bm5cO2t1uDc/WOOm4ylR5LI/AAAAAAAADBE/2Ms5D6uZCfg8Ci4OMgkNgvvioQiHMkfXwCPcB/s320/IMAG3480.jpg" width="320" /></a></div><br /></div><div style="text-align: justify;"><br /><br />It may not look like much, but the whole frame, once everything was tightened down is verry sturdy and can take quite a beating from that stepper.<br /><br />The black cylindrical thing is a home-made shaft coupler. I had some black delrin around that I bore on either side, to allow the 6.35 mm stepper shaft to couple to some M8 threaded rod. To keep the shafts from turning inside the coupler, I drilled &nbsp;two 6mm holes in the side of the shaft coupler then put in some&nbsp;<a href="http://www.tme.eu/ro/details/b4_bn903/inserturi-filetate/bossard/m4bn903/">brass inserts</a>. Two M4 screws go into the inserts, locking the shafts to the coupler.<br /><br />On the threaded rod I put some nuts as spacers and some Gardena hose adapters of some sort (the grey plastic things), that just happened to be the right shape to keep the ETD49 bobbin in place.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-fmex_5m1qcg/WOOuoGkMi4I/AAAAAAAADBk/nRrZPhDrETwuhzfGG_nEwT1PISn7KTGNACPcB/s1600/IMAG3619.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-fmex_5m1qcg/WOOuoGkMi4I/AAAAAAAADBk/nRrZPhDrETwuhzfGG_nEwT1PISn7KTGNACPcB/s320/IMAG3619.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Mhf74S6BjeI/WOOuoLu3omI/AAAAAAAADBk/A4sQ8GL7kDIYjBhaa_cM3ElAAAiktjHJACPcB/s1600/IMAG3620.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-Mhf74S6BjeI/WOOuoLu3omI/AAAAAAAADBk/A4sQ8GL7kDIYjBhaa_cM3ElAAAiktjHJACPcB/s320/IMAG3620.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"></div>&nbsp;I've also cut a slot in each of the grey plastic retainers and filed a mating pertrusion in the metal washers so that they wouldn't slip and turn ith the main stepper shaft. Of course, the plastic thingys will eventually be replaced with some proper 3D printed retainers, but who knows when that will be.<br /><div class="separator" style="clear: both; text-align: center;"></div><br /><br /></div><div style="text-align: justify;"><span style="font-size: large;"><b>Sharing is caring</b></span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">All the files for this build can be found on my <a href="https://github.com/catt87/Coil-Winder" target="_blank">GitHub</a> page. These include the code for the Arduino, the SolidWorks and STL files for the optical rotary thingy and whatever else I may find useful to throw in there.</div><div style="text-align: justify;">As always, you can enjoy the full splendor of crappy quality pictures of the build <a href="https://goo.gl/photos/rDPLzEhF4mD1qFbX9">here.</a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-38852465195369055722017-03-26T16:02:00.000+03:002017-03-26T16:02:03.058+03:00TwinTeeth Plus Build Log - Part 2&nbsp; &nbsp; <br /><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; This is an update on the <a href="http://www.diyouware.com/" target="_blank">TwinTeeth</a> build that I'm doing. You can check out the previous part <a href="http://electronicsplayground.blogspot.ro/2016/11/twinteeth-plus-build-log-part-1.html" target="_blank">here</a>.</div><div style="text-align: justify;"> &nbsp; &nbsp;</div><div style="text-align: justify;">First, I have to admit that &nbsp;molding your own ACME nuts is something far better than buying &nbsp;them. All bought ones have an unsatisfactory amount of play, and when dealing with lasers, play and backlash is the bane of one's existence.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp;Not being one to take anyone's word for granted, I initially bought some Nylon-MoS2 (Mylon-Molybdenum disulphide) ACME nuts, and though the person I talked to un the phone said it was done on a lathe, with an ACME tap, the end result is...well, shitty..</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-MXNOlYiDtaE/WNer1hQ3hUI/AAAAAAAAC-s/8t6ZNdC2m-QblrsvTlipR5kg0Fgj7v_IgCPcB/s1600/IMAG3592.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://4.bp.blogspot.com/-MXNOlYiDtaE/WNer1hQ3hUI/AAAAAAAAC-s/8t6ZNdC2m-QblrsvTlipR5kg0Fgj7v_IgCPcB/s400/IMAG3592.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp;They may look the part, but I measured up to 0.4 mm (15.8 thousandths for the imperial fanboys) slop in these bad boys. To say it's unacceptable &nbsp;is a serious understatement.</div><div style="text-align: justify;">Also, bronze ACME nuts won't do any better....Unless you do you own tapping on a lathe and get them to exactly fit the screw. But since I don't have a lathe....resin casting it is.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; I've tried several resins, from cheap and readily available ones to expensive cans of the stuff.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">First off, I used this kind of resin:</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-EqOm8H2_ZTI/WNer1jx17PI/AAAAAAAAC-s/X49rLmqEqPoWnsPyrmXvzhzVLm097c2XQCPcB/s1600/IMAG3593.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-EqOm8H2_ZTI/WNer1jx17PI/AAAAAAAAC-s/X49rLmqEqPoWnsPyrmXvzhzVLm097c2XQCPcB/s320/IMAG3593.jpg" width="320" /></a></div><br />It's a &nbsp;two-part putty-like resin. Just cut as much as you need and knead untill the colour is uniform. Unfortunately, although this cured rock-hard, it was very brittle and couldn't even take it out of the mold without flaking it or breaking it into several pieces. This was the biggest of them:<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-9oBaaicf6uM/WNer1qTm3qI/AAAAAAAAC-s/pRY7z04-DYwwDrldU3ycIq4xDRjyFn7qACPcB/s1600/IMAG3595.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-9oBaaicf6uM/WNer1qTm3qI/AAAAAAAAC-s/pRY7z04-DYwwDrldU3ycIq4xDRjyFn7qACPcB/s320/IMAG3595.jpg" width="320" /></a></div><br />&nbsp; &nbsp;Though it came out the way it did, I still could run the half-nut on the screw...by just holding it with my hand. Unfortunately, after &nbsp;taking the nut from the bottom of the screw to the top, with only hand-pressure applied to the half-nut to engage the screw, I noticed that the ACME screw was stripping away material from the bearing surface of the half-nut. A lot of material. Needless to say, that's a big No-No.<br /><br />So, I considered this alternative:<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-AOTqhKTjnfA/WNer1p_w6CI/AAAAAAAAC-s/VUMbhdxlZsc7L2TFAh9P8Hn0vPk1juDAACPcB/s1600/IMAG3594.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-AOTqhKTjnfA/WNer1p_w6CI/AAAAAAAAC-s/VUMbhdxlZsc7L2TFAh9P8Hn0vPk1juDAACPcB/s320/IMAG3594.jpg" width="320" /></a></div><br /><div style="text-align: justify;">but after &nbsp;seeing how the cured resin was just a bit on the stretchy side, I refused to give it any further &nbsp;thought.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Finally, I bought some expensive cans of a two part resin and some bronze powder. 250 grams of the bronze powder were about 23 Euros and 500 grams of resin was aroud 30 Euros.</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Mf5OF4l2Mzs/WNewqKKbkFI/AAAAAAAAC_8/FeBZr3uI8hQQdy2bq1dHkqIIkmjHGd-eACPcB/s1600/IMAG3601.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-Mf5OF4l2Mzs/WNewqKKbkFI/AAAAAAAAC_8/FeBZr3uI8hQQdy2bq1dHkqIIkmjHGd-eACPcB/s320/IMAG3601.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-XCf_BhaEl8g/WNewqBLuwyI/AAAAAAAAC_8/LyYue7spj-00yj7ivML65KXatdpokQg3ACPcB/s1600/IMAG3603.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://4.bp.blogspot.com/-XCf_BhaEl8g/WNewqBLuwyI/AAAAAAAAC_8/LyYue7spj-00yj7ivML65KXatdpokQg3ACPcB/s400/IMAG3603.jpg" width="266" /></a></div><br /><div style="text-align: justify;">Now, just like in any cake recipe, it's essential to mix the right ammounts so that at the end, you aren't left crying over spilled....resin.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">For the initial batch, I mixed 41 grams of A-part resin with 24 grams of B-part resin. I did this because first, the resin has a working time of up to 30 minutes and second, I read in a few places it's better to catalyze the resin first whenever you want to mix in metal powders.</div><div style="text-align: justify;">Next, I mixed in about 7 grams of the bronze powder and about 1 gram of graphite powder.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Now, some of you keen-minded fellows may find that 41 g and 24 g means a whole lot of resin. And you'd be right of course. I mixed WAY more that I needed for 3 moulds. Something like 10 gr. of A resing and 6 gr. of B resin would have been sufficient. Oh wel... live and learn... and cry your heart out for all that wasted resin.</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-COHkNtiyMDc/WNer1pJA43I/AAAAAAAAC-s/PCQqc2yilXEtL2l49MotZEVzgeSLDqWkgCPcB/s1600/IMAG3514.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-COHkNtiyMDc/WNer1pJA43I/AAAAAAAAC-s/PCQqc2yilXEtL2l49MotZEVzgeSLDqWkgCPcB/s320/IMAG3514.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-Vn2cCj8_3Vc/WNer1oBuOkI/AAAAAAAAC-s/5CHQRbOeUwQg_HrmJaOjkn7Hn3eD9em4QCPcB/s1600/IMAG3515.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-Vn2cCj8_3Vc/WNer1oBuOkI/AAAAAAAAC-s/5CHQRbOeUwQg_HrmJaOjkn7Hn3eD9em4QCPcB/s320/IMAG3515.jpg" width="320" /></a></div><br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-o0PZmj89tG4/WNer1tHIAxI/AAAAAAAAC-s/6IyC0SPczO0wjgMJ1AV4ZYFFZkHe-PGEgCPcB/s1600/IMAG3521.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-o0PZmj89tG4/WNer1tHIAxI/AAAAAAAAC-s/6IyC0SPczO0wjgMJ1AV4ZYFFZkHe-PGEgCPcB/s320/IMAG3521.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-lYfKEvWuFVc/WNer1nKaxKI/AAAAAAAAC-s/tR5jsFK4_IgueKB5PL2ww_Y0WhLym46cACPcB/s1600/IMAG3522.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-lYfKEvWuFVc/WNer1nKaxKI/AAAAAAAAC-s/tR5jsFK4_IgueKB5PL2ww_Y0WhLym46cACPcB/s320/IMAG3522.jpg" width="320" /></a></div><br /><br /><div style="text-align: justify;">While the resin cured, I started putting together the rest of the frame.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Apparently, the people I ordered the linear rods from didn't have a bottoming tap, so though the hole was 20mm deep, the threaded part was only 5mm deep. So I had to cut and grind 12 M4x16 screws to about 7 or 8 mm in length. Not really pleasant, but in a pinch, it did the job. The alternative was to order some M4x8 screws, which didn't really make &nbsp;a lot of sense. Oh, and I just used a pair of pliers to get the screws lo length. Low-tech works every time.</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-Z15owZKW3PY/WNer1oa5F5I/AAAAAAAAC-s/8NQfk8sOjGAK4B0zP0xCPJN9JyEfQCVgACPcB/s1600/IMAG3525.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-Z15owZKW3PY/WNer1oa5F5I/AAAAAAAAC-s/8NQfk8sOjGAK4B0zP0xCPJN9JyEfQCVgACPcB/s320/IMAG3525.jpg" width="213" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-OYh7vwu_IBU/WNer1hCQI3I/AAAAAAAAC-s/zldtI-y3qFckUVf0carKCSvFSMODrDiMQCPcB/s1600/IMAG3528.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-OYh7vwu_IBU/WNer1hCQI3I/AAAAAAAAC-s/zldtI-y3qFckUVf0carKCSvFSMODrDiMQCPcB/s320/IMAG3528.jpg" width="320" /></a></div><br /><br />The aluminium plates were all drilled and chamfered and once everything was tightened, the frame was really stiff. Remember, I used 2mm aluminium plate instead of 3mm, so I had some initial &nbsp;worries regarding this.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-LcDMZwczW1U/WNer1iZujeI/AAAAAAAAC-s/pFo5YYO6htM_66yN9b4EPPUosQfx2_u3gCPcB/s1600/IMAG3533.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-LcDMZwczW1U/WNer1iZujeI/AAAAAAAAC-s/pFo5YYO6htM_66yN9b4EPPUosQfx2_u3gCPcB/s320/IMAG3533.jpg" width="213" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-mO6UtTwQ6XM/WNer1lO4aYI/AAAAAAAAC-s/YjZyk8chzS8aFbs1N3qqz7XekReYiHZPACPcB/s1600/IMAG3536.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-mO6UtTwQ6XM/WNer1lO4aYI/AAAAAAAAC-s/YjZyk8chzS8aFbs1N3qqz7XekReYiHZPACPcB/s320/IMAG3536.jpg" width="320" /></a></div><br /><br /><div style="text-align: justify;">I also bought some 6000ZZ bearings and fitted them to the lead screw supports. I kind of goofed up on the diameter of the hole for the bearing, but since I already had printed the three lead screw supports, I went DIY on it's ass and wrapped the outside of the bearings in some kapton tape. This made the bearings fit nice and snug. That's one way of solving it.</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-fY3YtRiYSrI/WNer1m9lJ_I/AAAAAAAAC-s/9Rvrsmhqt0Y4c_TujkFSEiiSnRU0rXVTgCPcB/s1600/IMAG3546.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-fY3YtRiYSrI/WNer1m9lJ_I/AAAAAAAAC-s/9Rvrsmhqt0Y4c_TujkFSEiiSnRU0rXVTgCPcB/s320/IMAG3546.jpg" width="320" /></a></div><br /><br /><div style="text-align: justify;">About 24 hours after the initial pour, I &nbsp;took out the resin castings from the mould, and the results were....less than impressive:</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-rK6DsAm9Vg8/WNer1kOs5oI/AAAAAAAAC-s/aKDfaZSV5VUh_7emTcNgj05-JqJxO7DWgCPcB/s1600/IMAG3537.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-rK6DsAm9Vg8/WNer1kOs5oI/AAAAAAAAC-s/aKDfaZSV5VUh_7emTcNgj05-JqJxO7DWgCPcB/s320/IMAG3537.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-LQfrHcHL83I/WNer1tDak4I/AAAAAAAAC-s/LAEbuQY3rBgJXM16dt9Sz5MgmRc0bbJ8ACPcB/s1600/IMAG3538.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-LQfrHcHL83I/WNer1tDak4I/AAAAAAAAC-s/LAEbuQY3rBgJXM16dt9Sz5MgmRc0bbJ8ACPcB/s320/IMAG3538.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-V9d8vOf7VxY/WNer1r9Ud4I/AAAAAAAAC-s/z6NlJvdb804K1mnaDAXGAgSY7u8vAhC2QCPcB/s1600/IMAG3540.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-V9d8vOf7VxY/WNer1r9Ud4I/AAAAAAAAC-s/z6NlJvdb804K1mnaDAXGAgSY7u8vAhC2QCPcB/s320/IMAG3540.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-N1fBw3C831g/WNer1q2KejI/AAAAAAAAC-s/Qe_2dSeaKS00RN2ut0AVVQXxgC4f7Uh7ACPcB/s1600/IMAG3543.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-N1fBw3C831g/WNer1q2KejI/AAAAAAAAC-s/Qe_2dSeaKS00RN2ut0AVVQXxgC4f7Uh7ACPcB/s320/IMAG3543.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-e6t_SJOEBs0/WNer1stvOGI/AAAAAAAAC-s/SSvCStB-28ovgmVhRxOSa6EuejpAX2P4gCPcB/s1600/IMAG3544.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-e6t_SJOEBs0/WNer1stvOGI/AAAAAAAAC-s/SSvCStB-28ovgmVhRxOSa6EuejpAX2P4gCPcB/s320/IMAG3544.jpg" width="320" /></a></div><br /><br /><div style="text-align: justify;">&nbsp; &nbsp; Because there were two stakes in the mould, for the mounting holes, the castings came out in pieces. But that was the least of my worries.... because the resin was really runny and thin, it allowed the bronze powder to sink to the bottom, instead of being uniformly dispersed into the resin, hence the gold colour on the back side of the castings. The graphite poder however seems to have been pretty well incorporated into the resin.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; So, for the next try, I'm going to have to do some experimenting.... I'm thinking one way would be to use less resin and add so much bronze powder, so that the resin will only serve to bond the bronze particles together, resulting in a casting that is mostly bronze powder (80 % bronze maybe?).&nbsp;</div><div style="text-align: justify;">Another option, just &nbsp;add &nbsp;something like 50 percent bronze powder to the resin mix and hope that wil thicken the resin enough to still be able to be poured but also not let the bronze settle to the bottom.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; However, despite this drawback, I did manage to try out two half-nuts on an ACME screw, and the result was pretty amazing.... Absolutely no slop in the nut. And though there was no bronze on the bearing surface of the half-nut, it moved very smoothly on the screw and without any (noticeable) resin material being stripped away by the screw, like with the first resin experiment I did.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; As a sidenote, a thing to consider when doing this is LUBRICATION of the moulds. Do not leave any part of the inside of the mould un-lubricated (is that a word?) It will be a nightmare to get the mould casting out.&nbsp;</div><div style="text-align: justify;">I smuthered the inside of my moulds in silicon grease and also dabed graphite powder onto the grease. I it hadn;t been for the two mounting posts in the mould, I think the castings would have came out in one piece.</div><div style="text-align: justify;">&nbsp; &nbsp;And if worse comes to pass, you can always print your moulds at about 10 Percent infill, allowing you to sacrifice the mould to take out the casting.</div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-24489068908112225242017-01-08T19:09:00.001+02:002017-01-08T19:09:33.908+02:00Interstate Electronics Corporation SPG-800 Signal Generator Teardown<span style="font-size: large;">&nbsp; &nbsp; &nbsp;</span><br /><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp; &nbsp; Well. it turns out that Christmas came a bit later this year. Probably &nbsp;one of the&nbsp;reindeers had a flat hoof, or something.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-fb6TcTG5b_A/WHI-ihd9aOI/AAAAAAAACls/hyoeh3c-b_UfWzNGcrFOXBLVtYv1DoLBACPcB/s1600/20170107_222611.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="225" src="https://1.bp.blogspot.com/-fb6TcTG5b_A/WHI-ihd9aOI/AAAAAAAACls/hyoeh3c-b_UfWzNGcrFOXBLVtYv1DoLBACPcB/s400/20170107_222611.jpg" width="400" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-X-y6t2rfwjw/WHI-isY5VMI/AAAAAAAACls/05P1Oz6-fA8h7Wsy05wjRc6NhliajQGfwCPcB/s1600/20170107_222632.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="225" src="https://3.bp.blogspot.com/-X-y6t2rfwjw/WHI-isY5VMI/AAAAAAAACls/05P1Oz6-fA8h7Wsy05wjRc6NhliajQGfwCPcB/s400/20170107_222632.jpg" width="400" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; OK, so I bought myself a signal generator for the measly sum of 70 Euros, including shipping. The guy I bought it from said the unit didn't work. No problem, I said to &nbsp;myself. It'll make a nice organ donor for other projects. Probably filled with all kinds of goodness inside.....matched JFET pairs maybe.... a nice 10 MHz reference. I was drooling over it.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">Now, let me tell you, when it came, I almost had a hernia. It's heavy as frig....about 20 Kilos worth of 2 DIN (I guess) rackable signal generator.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;So, I got the beast in the house (all the way up to the 5th floor and no elevator, mind you) and first thing I looked at was the fuse....which, of course, was nice and toasted. Before replacing it, I looked at the mains voltage selection switch. My optimism spiked when I saw it was set to 230 V AC.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">So, now, knowing that the main transformer and PSU inside it might be OK, I replaced the fuse, turned it on and....nothing, obviously.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;So, following the "Thow shall always measure voltages" rule, I got the DMM out and first thing I measured was the input to the transformer. It measured 0 V on its input.</span></div><div style="text-align: justify;"><span style="font-size: large;">Seeing as how the on/off switch was all gooey, I measured the voltage on its pins. Nothing as well.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">Ok, I'll bite.... I preceeded to desolder the wires from the switch, rummaged through my junk pile and found a suitable replacement then soldered back the wires on that one.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; &nbsp;Because I didn't find the appropriate fuse size, I cobbled something with I could find. No pretty, but it did the job.</span></div><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eflWQBSDP0c/WHI-imEwgjI/AAAAAAAACls/KgEPgn2yUTw7ehciib2R3OIaIZsjVjEOACPcB/s1600/20170108_140125.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="225" src="https://1.bp.blogspot.com/-eflWQBSDP0c/WHI-imEwgjI/AAAAAAAACls/KgEPgn2yUTw7ehciib2R3OIaIZsjVjEOACPcB/s400/20170108_140125.jpg" width="400" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Yes, apparently, it was just that simple. So, now that I had a working Signal generator, let's see what it can do.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">The first thing I noticed when turning it on was how loud the fan was. It sounded as if I had a tractor plowing right next to me.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Unfortunately, I couldn't fin any FREE user's manual or service manual for this unit. There is on on eBay for sale, but as of writing this , it cost about 80 dollars including shipping. Needless to say, the guy selling it can just shove it, I ain't paying that much. I;m sensible for these kinds of things.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Ok, so from playing around with the unit, it looks like it can do a frequency range from about 10 mHz all the way up to (what should be) 10 MHz. If it goes higher, I couldn't find the right combination of random key presses tht made it go beyond 10 MHz.</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp; Amplitude wise, looks like it can go as low as 100 mVpp and as high as 100 Vpp, all &nbsp;into 50 Ohms. Yes, really. At least that's what my scope measures, anyway.</span></div><div style="text-align: justify;"><span style="font-size: large;">On the output BNC, it didn't mention anything about it being 50 Ohms, but I just presumed it was. Also, if I feed the output directly into the scope, without a 50 Ohm termination, the square waveforms look distorted.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">So, what else can this beast do? Well, it has you basic Sine, Square, Triangle and Pulse Width waveforms. Also, it has a nice and handy Burst Mode. As for the rest, I really can't say. I probably need &nbsp;to RTFM.... If only I could find one that didn't cost more that what I paid for the unit itself.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">And now, on to our scheduled Teardown:</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">The unit has a modular construction. And judging from the number of empty slots, looks like you could attach a whole freaking lot of options to this generator. Too bad I only got the basic version.</span></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-xtO5jGAxNzg/WHI-irTgz-I/AAAAAAAACls/QWRSbgicD08ijSZgjViYnoxzMiTbvhh8gCPcB/s1600/20170108_121826.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="400" src="https://2.bp.blogspot.com/-xtO5jGAxNzg/WHI-irTgz-I/AAAAAAAACls/QWRSbgicD08ijSZgjViYnoxzMiTbvhh8gCPcB/s400/20170108_121826.jpg" width="225" /></span></a></div><div class="separator" style="clear: both; text-align: center;"><span style="font-size: large;"><br /></span></div><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-HRMCCaR_Oss/WHI-iueVenI/AAAAAAAACls/SOy0drKKOzAp-_fWcunB1jSr8qzZiZJHwCPcB/s1600/20170108_121903.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://2.bp.blogspot.com/-HRMCCaR_Oss/WHI-iueVenI/AAAAAAAACls/SOy0drKKOzAp-_fWcunB1jSr8qzZiZJHwCPcB/s320/20170108_121903.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-aFF3OyzCifc/WHI-ij5vZfI/AAAAAAAACls/NU40vkNikb0Nit01nHGEWKTTPNN_yZs2gCPcB/s1600/20170108_121913.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-aFF3OyzCifc/WHI-ij5vZfI/AAAAAAAACls/NU40vkNikb0Nit01nHGEWKTTPNN_yZs2gCPcB/s320/20170108_121913.jpg" width="320" /></span></a></div><div class="separator" style="clear: both; text-align: center;"><span style="text-align: start;"><span style="font-size: large;"><br /></span></span></div><div class="separator" style="clear: both; text-align: justify;"><span style="text-align: start;"><span style="font-size: large;">Next up is the PSU board. Amazingly enough, for a unit that's well over 30 years old, the caps look OK. All of them.</span></span></div><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/--rme2KfqQEM/WHJEmV0RFNI/AAAAAAAACvI/JHE4Pk-rdRMnIQ6i9y4VECZ7eowdAnIVACPcB/s1600/PSU%2B-%2B%2B%252815%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://4.bp.blogspot.com/--rme2KfqQEM/WHJEmV0RFNI/AAAAAAAACvI/JHE4Pk-rdRMnIQ6i9y4VECZ7eowdAnIVACPcB/s320/PSU%2B-%2B%2B%252815%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-I14u6xtemMo/WHJEmZLdo3I/AAAAAAAACvI/_PdYdXo8s1chUsRnFXOYAwgtxirWtmR9gCPcB/s1600/PSU%2B-%2B%2B%252812%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://2.bp.blogspot.com/-I14u6xtemMo/WHJEmZLdo3I/AAAAAAAACvI/_PdYdXo8s1chUsRnFXOYAwgtxirWtmR9gCPcB/s320/PSU%2B-%2B%2B%252812%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-Os9lTmHTYao/WHJEmTJmh-I/AAAAAAAACvI/PgNdAGpGy8YfpQNOc5x1hH5BtdXar7SYACPcB/s1600/PSU%2B-%2B%2B%25283%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-Os9lTmHTYao/WHJEmTJmh-I/AAAAAAAACvI/PgNdAGpGy8YfpQNOc5x1hH5BtdXar7SYACPcB/s320/PSU%2B-%2B%2B%25283%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-h4-I6VOAWqs/WHJEmWWTYRI/AAAAAAAACvI/-W_QSiy6KZUI7bJ6902fPqDNXZ3j9sjrgCPcB/s1600/PSU%2B-%2B%2B%252817%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-h4-I6VOAWqs/WHJEmWWTYRI/AAAAAAAACvI/-W_QSiy6KZUI7bJ6902fPqDNXZ3j9sjrgCPcB/s320/PSU%2B-%2B%2B%252817%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><span style="font-size: large;">&nbsp;The next board to get lifted out, after who knows how any years, is the A2 "Program Logic Card"</span><br /><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-UsYdoJL8P2M/WHJAFFsHp4I/AAAAAAAACnM/rjBOalWuXF8l5jY_0ZJ2AbmK99YBo6VZgCPcB/s1600/20170108_122744.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="225" src="https://1.bp.blogspot.com/-UsYdoJL8P2M/WHJAFFsHp4I/AAAAAAAACnM/rjBOalWuXF8l5jY_0ZJ2AbmK99YBo6VZgCPcB/s400/20170108_122744.jpg" width="400" /></span></a></div><span style="font-size: large;"><br /></span><span style="font-size: large;">Looks like this is some glue logic, because the board if full of buffers, MUXs and other 74LS family logic.</span><br /><span style="font-size: large;"><br /></span><span style="font-size: large;">Next up is the A20 - IEEE-488 interface card.</span><br /><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-eq-27d8vEdc/WHJDwbAi2iI/AAAAAAAACts/zqbYOYlPPI8Yht-srpTVqwHVOEPzu81zACPcB/s1600/A20%2B-%2B%2B%25285%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-eq-27d8vEdc/WHJDwbAi2iI/AAAAAAAACts/zqbYOYlPPI8Yht-srpTVqwHVOEPzu81zACPcB/s320/A20%2B-%2B%2B%25285%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-JsTBMwLV75Y/WHJDwX-SVAI/AAAAAAAACts/wnZPg6p-FSUIOCc2G_V0flpWB82nJvPvwCPcB/s1600/A20%2B-%2B%2B%25289%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-JsTBMwLV75Y/WHJDwX-SVAI/AAAAAAAACts/wnZPg6p-FSUIOCc2G_V0flpWB82nJvPvwCPcB/s320/A20%2B-%2B%2B%25289%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><span style="font-size: large;">Starting from the left corner, there's a DIP switch, for setting the address of the device, two resistor networks (that's what Google came up with): 316A622 and 316A302, and a whole bunch of logic gates. 74LS family, of course.</span><br /><span style="font-size: large;"><br /></span><span style="font-size: large;">Now we're starting to get into the meat of it. A7 - Question Mark Card</span><br /><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iu3i3yRWxM8/WHJBWaLyuLI/AAAAAAAACqw/AVKsCinbMrQiddV9R5Dsu0ykOA7vIS1WACPcB/s1600/A7%2B-%2B%2B%25282%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-iu3i3yRWxM8/WHJBWaLyuLI/AAAAAAAACqw/AVKsCinbMrQiddV9R5Dsu0ykOA7vIS1WACPcB/s320/A7%2B-%2B%2B%25282%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-pYt5oKJfQmc/WHJBWRCz4iI/AAAAAAAACqw/VyioCwtCBhMfEeBqBJh_AX7uizhhH_tcwCPcB/s1600/A7%2B-%2B%2B%25284%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-pYt5oKJfQmc/WHJBWRCz4iI/AAAAAAAACqw/VyioCwtCBhMfEeBqBJh_AX7uizhhH_tcwCPcB/s320/A7%2B-%2B%2B%25284%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-j8IGBk6PsKw/WHJBWR-a2bI/AAAAAAAACqw/uR8AyD2P1H88eL0oU-7J2qo4MRxcA90tACPcB/s1600/A7%2B-%2B%2B%25285%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-j8IGBk6PsKw/WHJBWR-a2bI/AAAAAAAACqw/uR8AyD2P1H88eL0oU-7J2qo4MRxcA90tACPcB/s320/A7%2B-%2B%2B%25285%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-8XKvIV1MTGU/WHJBWdnt5nI/AAAAAAAACqw/nc8cnPeIUaUZVoCpcxzz1u9613mUhOPjwCPcB/s1600/A7%2B-%2B%2B%25287%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-8XKvIV1MTGU/WHJBWdnt5nI/AAAAAAAACqw/nc8cnPeIUaUZVoCpcxzz1u9613mUhOPjwCPcB/s320/A7%2B-%2B%2B%25287%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;">&nbsp;Nope, no idea what "S/S" means or what it does. But it looks cool, doesn't it?</span></div><div style="text-align: justify;"><span style="font-size: large;">&nbsp;Maybe signal conditioning? Or maybe it's something that has to do with the DC Offsets and stuff?</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">Next on the list is the A8 - Frequency Syhtesizer Card</span></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-NfptsDe7Aeo/WHJBsJXD6lI/AAAAAAAACos/vu61ElKK4z4zzS1xTjK9hLHpBEhlAWm0QCPcB/s1600/A8%2B-%2B%2B%25281%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://4.bp.blogspot.com/-NfptsDe7Aeo/WHJBsJXD6lI/AAAAAAAACos/vu61ElKK4z4zzS1xTjK9hLHpBEhlAWm0QCPcB/s320/A8%2B-%2B%2B%25281%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-YWLIUJK6DJM/WHJBsPsYIlI/AAAAAAAACos/ZvOrV8lGtcUaUG_iE-OptWmJIPrA_jzKACPcB/s1600/A8%2B-%2B%2B%25284%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-YWLIUJK6DJM/WHJBsPsYIlI/AAAAAAAACos/ZvOrV8lGtcUaUG_iE-OptWmJIPrA_jzKACPcB/s320/A8%2B-%2B%2B%25284%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-P9Z-KoBSwok/WHJBsPinheI/AAAAAAAACos/w0IMsJ4y4cs6TGD8tUmUm2oav0AxxMHWgCPcB/s1600/A8%2B-%2B%2B%25286%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-P9Z-KoBSwok/WHJBsPinheI/AAAAAAAACos/w0IMsJ4y4cs6TGD8tUmUm2oav0AxxMHWgCPcB/s320/A8%2B-%2B%2B%25286%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-2rmFlkrP7Iw/WHJBsNG-MCI/AAAAAAAACos/l-a4Zikm_mYp5gt8R8-0UhLUQcsTAB29QCPcB/s1600/A8%2B-%2B%2B%25288%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-2rmFlkrP7Iw/WHJBsNG-MCI/AAAAAAAACos/l-a4Zikm_mYp5gt8R8-0UhLUQcsTAB29QCPcB/s320/A8%2B-%2B%2B%25288%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-5i-D2XM_its/WHJBsE2PPYI/AAAAAAAACos/IL0iiqFnxMgq_3lt8EcSVHOjeYPNmsh1QCPcB/s1600/A8%2B-%2B%2B%252810%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://2.bp.blogspot.com/-5i-D2XM_its/WHJBsE2PPYI/AAAAAAAACos/IL0iiqFnxMgq_3lt8EcSVHOjeYPNmsh1QCPcB/s320/A8%2B-%2B%2B%252810%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;">You gotta love those hand drawn traces. Finally, we get to see some of that goodness I was hoping.</span></div><div style="text-align: justify;"><span style="font-size: large;">The digital part has the usual logic gates, flip-flops, etc. The analog part... well...</span></div><div style="text-align: justify;"><span style="font-size: large;">The main part is the <a href="http://www.datasheets360.com/pdf/5240154412110444418" target="_blank">AM26S02PC </a>&nbsp;Monostable Vibrator.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">This, together with that ferrite and &nbsp;some &nbsp;<a href="http://pdf1.alldatasheet.com/datasheet-pdf/view/66309/INTERSIL/CA3039.html" target="_blank">CA3039</a> diode arrays seem to make up what would be a ring modulator. I don't know too much about RF stuff or frequency symthesizers, so if anyone has a better idea of what the synthesizer might actually look loke, pleas leave a comment. I'm really interested in how this thing works. If only I had a manual for this thing.</span></div><div style="text-align: justify;"><span style="font-size: large;">Also, some keen observers might see that there's a whole boatload of diodes on this part of the board and I doubt they're all &nbsp;Zeners.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">The next board is the Waveform Selection A9 Card.</span></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-fVNeV7u5fFU/WHJCBRNLKdI/AAAAAAAACqo/2QTph5YXS8ggMfRpbMQLQEbYkY2Aky0lgCPcB/s1600/A9%2B-%2B%2B%25281%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-fVNeV7u5fFU/WHJCBRNLKdI/AAAAAAAACqo/2QTph5YXS8ggMfRpbMQLQEbYkY2Aky0lgCPcB/s320/A9%2B-%2B%2B%25281%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-AYK7BiV9VBo/WHJCBbcg0WI/AAAAAAAACqo/tsHpwGFbuL48LnHO9b58r1Ta-36DEUPawCPcB/s1600/A9%2B-%2B%2B%25283%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://4.bp.blogspot.com/-AYK7BiV9VBo/WHJCBbcg0WI/AAAAAAAACqo/tsHpwGFbuL48LnHO9b58r1Ta-36DEUPawCPcB/s320/A9%2B-%2B%2B%25283%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-ZrQdv6lqaks/WHJCBZLGNVI/AAAAAAAACqo/ItepU74zuZgN3KteV2s6X9PpU4zbkXZ6QCPcB/s1600/A9%2B-%2B%2B%25286%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://4.bp.blogspot.com/-ZrQdv6lqaks/WHJCBZLGNVI/AAAAAAAACqo/ItepU74zuZgN3KteV2s6X9PpU4zbkXZ6QCPcB/s320/A9%2B-%2B%2B%25286%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-ve_okSeTMlI/WHJCBVc_u4I/AAAAAAAACqo/Wo5-Ua_uvc0rP5tXzcLy6p6c8o-C0fT-gCPcB/s1600/A9%2B-%2B%2B%25289%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://2.bp.blogspot.com/-ve_okSeTMlI/WHJCBVc_u4I/AAAAAAAACqo/Wo5-Ua_uvc0rP5tXzcLy6p6c8o-C0fT-gCPcB/s320/A9%2B-%2B%2B%25289%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-XEQ6lqWtsmA/WHJCBd_kywI/AAAAAAAACqo/R9E-FoHVVfU5Ap7kN0dsDvYDs77aSYMCwCPcB/s1600/A9%2B-%2B%2B%252811%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-XEQ6lqWtsmA/WHJCBd_kywI/AAAAAAAACqo/R9E-FoHVVfU5Ap7kN0dsDvYDs77aSYMCwCPcB/s320/A9%2B-%2B%2B%252811%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-KgRlbWXo988/WHJCBdAaQaI/AAAAAAAACqo/MDDRx0ottf0DxVZ4S0tn8N2yczucB7TFgCPcB/s1600/A9%2B-%2B%2B%252827%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-KgRlbWXo988/WHJCBdAaQaI/AAAAAAAACqo/MDDRx0ottf0DxVZ4S0tn8N2yczucB7TFgCPcB/s320/A9%2B-%2B%2B%252827%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">From the looks of things, it looks like the board is mainly switching some stuff in and out, i.e. ony selecting the appropriate waveform. The yellow cylinders are most likely relays and the two 8-pin ICs are <a href="http://www.ti.com/lit/ds/symlink/ds75450.pdf" target="_blank">DS75451N</a> drivers, for said relays.</span></div><div style="text-align: justify;"><span style="font-size: large;">The bigger IC on the far right is a <a href="http://radio-hobby.org/uploads/datasheet/641/ca30/ca3086.pdf" target="_blank">CA3086</a>&nbsp;transistor array.</span></div><div style="text-align: justify;"><span style="font-size: large;">The three single line ICs are resistor networks. One might speculate that these together with the diodes make up some snubber for the relays' coils. Though this is arguable.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">The next card is the one that does all the heavy work - &nbsp;The Output Amplifier A10 Card</span></div><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-Zgdk6jmWUHQ/WHJCbQr1L7I/AAAAAAAACsM/b_2wbWYciVYpbjPL0BjdWVvESpyLjStdwCPcB/s1600/A10%2B-%2B%2B%25281%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-Zgdk6jmWUHQ/WHJCbQr1L7I/AAAAAAAACsM/b_2wbWYciVYpbjPL0BjdWVvESpyLjStdwCPcB/s320/A10%2B-%2B%2B%25281%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-nWF3DSMf1mg/WHJCbQ-sWzI/AAAAAAAACsM/VtMyVAuyfOohZZVJrxQ-VvGmjBmyxN-bgCPcB/s1600/A10%2B-%2B%2B%25283%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-nWF3DSMf1mg/WHJCbQ-sWzI/AAAAAAAACsM/VtMyVAuyfOohZZVJrxQ-VvGmjBmyxN-bgCPcB/s320/A10%2B-%2B%2B%25283%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aVRtmKkysmA/WHJCbWXx0YI/AAAAAAAACsM/LaxoAVMx2hURGMRFQgwMJuzNmvEC8xTqwCPcB/s1600/A10%2B-%2B%2B%25286%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-aVRtmKkysmA/WHJCbWXx0YI/AAAAAAAACsM/LaxoAVMx2hURGMRFQgwMJuzNmvEC8xTqwCPcB/s320/A10%2B-%2B%2B%25286%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-Rl5c15jR5Ko/WHJCbZ9yEEI/AAAAAAAACsM/EX2DBAsso7EnhqThzLgKQowDzVNZE8DNwCPcB/s1600/A10%2B-%2B%2B%25288%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://4.bp.blogspot.com/-Rl5c15jR5Ko/WHJCbZ9yEEI/AAAAAAAACsM/EX2DBAsso7EnhqThzLgKQowDzVNZE8DNwCPcB/s320/A10%2B-%2B%2B%25288%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-dJdP8qYF5Ho/WHJCbe09W-I/AAAAAAAACsM/eWl0BavdWYgyS4gMIV9KTJh4Y0iUEmSgACPcB/s1600/A10%2B-%2B%2B%25284%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-dJdP8qYF5Ho/WHJCbe09W-I/AAAAAAAACsM/eWl0BavdWYgyS4gMIV9KTJh4Y0iUEmSgACPcB/s320/A10%2B-%2B%2B%25284%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;">Some bus interface logic, a few Motorola <a href="http://www.datasheets360.com/pdf/-4331891609707459246" target="_blank">2N5160</a>&nbsp;and <a href="http://alltransistors.com/pdfview.php?doc=2n5109.pdf&amp;dire=_central" target="_blank">2N5109</a> RF transistors and some analog goodness make what is to be the generator's output board.</span></div><div style="text-align: justify;"><span style="font-size: large;">The front end of the amp is an RCA <a href="http://www.tradeofic.com/Circuit/4451-2_METER_IC_RF_AMPLIFIER_.html" target="_blank">CA3102E</a>&nbsp;differential amplifier IC.</span></div><div style="text-align: justify;"><span style="font-size: large;">Also notice the point-to-point connections in the third and fourth picture.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">And last, but not least, we have the (Amp?) DAC card - A11</span></div><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-IcfTkqmm2uY/WHJDAbbQ-gI/AAAAAAAACs8/ikwgD5smr946Vn2dXNcPf9vyzonGm8xFACPcB/s1600/A11%2B-%2B%2B%25281%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-IcfTkqmm2uY/WHJDAbbQ-gI/AAAAAAAACs8/ikwgD5smr946Vn2dXNcPf9vyzonGm8xFACPcB/s320/A11%2B-%2B%2B%25281%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-1-YoSJv8Ta8/WHJDAUQ4I_I/AAAAAAAACs8/df3p2P4qrmwyLp733eB8gT-bTncwWJJrgCPcB/s1600/A11%2B-%2B%2B%25284%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-1-YoSJv8Ta8/WHJDAUQ4I_I/AAAAAAAACs8/df3p2P4qrmwyLp733eB8gT-bTncwWJJrgCPcB/s320/A11%2B-%2B%2B%25284%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-0mxakwx9N1g/WHJDAeWQd6I/AAAAAAAACs8/fg8W4sg84xw5T15wSK6yKL9ebM6FwWN0gCPcB/s1600/A11%2B-%2B%2B%25285%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://2.bp.blogspot.com/-0mxakwx9N1g/WHJDAeWQd6I/AAAAAAAACs8/fg8W4sg84xw5T15wSK6yKL9ebM6FwWN0gCPcB/s320/A11%2B-%2B%2B%25285%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-iKFAj6eQbx8/WHJDATxr2pI/AAAAAAAACs8/E09zuJg42dUg-wH6ti3yPOT4aVY7RBy8gCPcB/s1600/A11%2B-%2B%2B%25286%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://4.bp.blogspot.com/-iKFAj6eQbx8/WHJDATxr2pI/AAAAAAAACs8/E09zuJg42dUg-wH6ti3yPOT4aVY7RBy8gCPcB/s320/A11%2B-%2B%2B%25286%2529.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-9HMZJLe9bBI/WHJDAaeQH7I/AAAAAAAACs8/i5R4Pa5Yt1QbWuOWucJLf8WnI5zs5pOyACPcB/s1600/A11%2B-%2B%2B%25289%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-9HMZJLe9bBI/WHJDAaeQH7I/AAAAAAAACs8/i5R4Pa5Yt1QbWuOWucJLf8WnI5zs5pOyACPcB/s320/A11%2B-%2B%2B%25289%2529.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><div style="text-align: justify;"><span style="font-size: large;">The usual bus interface and glue logic ICs. Boring.. But wait. What's this? an RCA &nbsp;<a href="http://datasheet.octopart.com/CA3130S-Harris-datasheet-38151400.pdf" target="_blank">CA3130S</a>. Now this is something. It's a metal can op-amp. But more that that, it's a PMOS input op-amp. Here's something you don't see every day. Well, I don't, anyway.</span></div><div style="text-align: justify;"><span style="font-size: large;">And some more Analog goodness - an &nbsp;<a href="http://www.datasheetarchive.com/dlmain/7c30457e78b5a9059ae0a78a85c6533a9f1cae/M/SN72558" target="_blank">SN72558P</a>&nbsp;op-amp</span></div><div style="text-align: justify;"><span style="font-size: large;">Ok, so maybe it's not something to write home about, but I thought I'd try and distract you fro the fact tht there is no actual DAC on this board. It might actually be on the board that's blted to the front panel. And I'm too lazy to actually take that out. Another option might be that all those resistors up there make an R-2R ladder DAC, but they all seem to have the same value, so that theory's shot.</span></div><div style="text-align: justify;"><span style="font-size: large;">So this board ight indeed be just a pre-amp for the signal coming from the DAC.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">It looks like the reference is a simple 1 MHz crystal olscillator. I might consider changing that &nbsp;to some TCXO or OCXO. We'll see.</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;"><span style="font-size: large;">Ok, so basically, I have a working unit, though there's still &nbsp;a lot of loose ends to it. For starters the amplitude &nbsp;and frequency are WAY off from what I set on the front panel.</span></div><div style="text-align: justify;"><span style="font-size: large;">For the frequency, there seems to be a ~2.5% to 3% deviation across all frequency ranges. For the output voltage.....well, the deviation is about 20 to 25% on all frequency ranges.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: large;">These might be simple, except there's a whole heapin' mess of trimmers. Yes, you've guessed it.. I really need a mannual for this thing.</span></div><span style="font-size: large;"><br /></span><span style="font-size: large;">Here's a few mre pics of the beast in action:</span><br /><span style="font-size: large;"><br /></span><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-AHT-9RQZAZs/WHI-ioGX6mI/AAAAAAAACls/5JNN7jGMwo4tKw-UStowyjfC6wAINnjyQCPcB/s1600/20170108_140522.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-AHT-9RQZAZs/WHI-ioGX6mI/AAAAAAAACls/5JNN7jGMwo4tKw-UStowyjfC6wAINnjyQCPcB/s320/20170108_140522.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-1k-3lLqWXSA/WHI-iu3BkbI/AAAAAAAACls/UnAuP9eU8wsHxAkkplf5fUsFnTVRMfupwCPcB/s1600/20170108_140510.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-1k-3lLqWXSA/WHI-iu3BkbI/AAAAAAAACls/UnAuP9eU8wsHxAkkplf5fUsFnTVRMfupwCPcB/s320/20170108_140510.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-0PLA1wmwQhE/WHI-irfSzpI/AAAAAAAACls/ty8RxJneONgaP4uxGyQNXnx9V2iyTViggCPcB/s1600/20170108_140404.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://2.bp.blogspot.com/-0PLA1wmwQhE/WHI-irfSzpI/AAAAAAAACls/ty8RxJneONgaP4uxGyQNXnx9V2iyTViggCPcB/s320/20170108_140404.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-qg1xWUuRw5A/WHI-ijxATII/AAAAAAAACls/oELQX5ciwvY8q2mwZRONY62d_IjguJCcwCPcB/s1600/20170108_140137.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://3.bp.blogspot.com/-qg1xWUuRw5A/WHI-ijxATII/AAAAAAAACls/oELQX5ciwvY8q2mwZRONY62d_IjguJCcwCPcB/s320/20170108_140137.jpg" width="320" /></span></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-iabHAdG3pmE/WHI-inoYnyI/AAAAAAAACls/IbfinWhLSiQ2K0YXgrn--kwSxVPxCS_zQCPcB/s1600/20170108_140356.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-size: large;"><img border="0" height="180" src="https://1.bp.blogspot.com/-iabHAdG3pmE/WHI-inoYnyI/AAAAAAAACls/IbfinWhLSiQ2K0YXgrn--kwSxVPxCS_zQCPcB/s320/20170108_140356.jpg" width="320" /></span></a></div><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;">In caase someone happens to have a manual for this thing and is willing to share, please contact me either by leaving a comment or on the blog's <a href="https://www.facebook.com/ElectronicsPlayground/" target="_blank">facebook</a> page. Thanks.</span><br /><span style="font-size: large;"><br /></span><span style="font-size: large;">If you'd like to see the full album of the teardown, &nbsp;<a href="https://goo.gl/photos/jbV9DNZTkuL1dTTk8" target="_blank">here</a>&nbsp;it is.</span><br /><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><span style="font-size: large;"><br /></span><br />Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-19795223832064744022016-11-04T11:47:00.001+02:002016-11-04T11:47:22.373+02:00TwinTeeth Plus Build Log - Part 1<div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp;</span></div><div style="text-align: justify;"><span style="font-family: inherit;"><span style="font-size: large;"><br /></span></span></div><div style="text-align: justify;"><span style="font-family: inherit;"><span style="font-size: large;">I want a PCB and I want it NOW!</span></span></div><div style="text-align: justify;"><span style="font-family: inherit;"><span style="font-size: large;"><br /></span></span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp; Have you ever had a burning need to design, layout then etch a 2 sided prototype PCB, at home, before you send it out to a PCB fab, to make sure everything is OK?</span></div><div style="text-align: justify;">Well, so have I.</div><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp; I came across a PCB "design bundle" that I really want to try out and &nbsp;build.&nbsp;</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">This will be &nbsp;the first in a line of blog entries, detailing my build process and review of this.&nbsp;</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">Because of it's open source nature (nice one guys, thanks!) I had everything I needed to modify and adapt my design to fit the parts that I had.&nbsp;</span></div><div style="text-align: justify;"><span style="font-family: inherit;">Therefore, along with these posts I will also upload the files for the parts that I redid, just in case someone happens to have some of the parts that I had.</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit; font-size: large;">...but first, some background on this</span></div><div style="text-align: justify;"><span style="font-family: inherit; font-size: large;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp; I've spent a few weeks looking around for ideas on how to PROPERLY make a device that moves on 2 or 3 axes and &nbsp;has a UV laser for a head. I wanted this to do a line-scan on a UV resin-coated PCB board, then etch it and have a prototype PCB done in &nbsp;a matter of 30-60 minutes.</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">I quickly came to the conclusion that a &nbsp;traditional gantry-style &nbsp;CNC machine wouldn't cut it, in terms of speed.</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp; So, thinking about other stuff that has a scanning laser, I thought about how fast laser printers work. Then I began looking at trying to control a mirror array from an actual laser printer.&nbsp;</span></div><div style="text-align: justify;"><span style="font-family: inherit;">In theory, it wouldn't be hard at all. Just have a hexagonal mirror spin on a spindle, shine a UV laser on it then pulse the laser so it will scan the board one line at a time. But, as always, the devil is in the details.&nbsp;</span></div><br /><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp; Suppose you have a PCB that's 10cm x 10cm. The laser position is fixed.&nbsp;</span><span style="font-family: inherit;">All you're doing is generating a scanning pattern with the hexagonal mirror. That means, that relative to the center point of the PCB, &nbsp;the laser beam will have to travel 5 cm in each direction (5 to the left and 5 to the right). This means that the beam length will be altered by ± 5 cm.&nbsp;</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">According to physics, if the length of the beam changes, that means that the focusing of the beam will change also.&nbsp;</span></div><div style="text-align: justify;"><span style="font-family: inherit;">What that means is, with a fixed focus, as would be the case in a scanning head, the beam will be focused in the middle of the board and it will be slightly out of focus on the edges of the board. If you have a laser beam that is not properly focused, it will leave behind an image that is blurry.&nbsp;</span></div><div style="text-align: justify;"><span style="font-family: inherit;">And if you're doing &nbsp;a board with, say, 0603 components on it, the pads will come out looking more like blobs of copper.</span></div><div style="text-align: justify;"><span style="font-family: inherit;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-family: inherit;">&nbsp; &nbsp; &nbsp; Of course, l</span><span style="font-family: inherit;">aser printers have the same issue. The way THEY solve this is &nbsp;they have &nbsp;an &nbsp;f-Theta lens in the beam path.</span></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; For those of us that don't have Stephen Hawking &nbsp;on speed-dial, an "f-Theta" lens &nbsp;will take the incoming FOCUSED &nbsp;beam of light and keep it focused, no matter the angle it's outputted at (or, put it another way, along the scanning path, &nbsp;the beam, it will be focused in any point)</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-T9BGeueLWf8/WBGfCmJw0mI/AAAAAAAACV8/-4dYF_cF7scjY4MkLGU_DoaWL6vLn3brACLcB/s1600/laser-processing-principle.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://1.bp.blogspot.com/-T9BGeueLWf8/WBGfCmJw0mI/AAAAAAAACV8/-4dYF_cF7scjY4MkLGU_DoaWL6vLn3brACLcB/s1600/laser-processing-principle.jpg" /></a></div><div style="text-align: justify;"><span style="font-size: xx-small;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Source: http://www.opli.net/opli_magazine/eo/2014/optotune-demonstrates-new-laser-processing-lens-aug-news/</span></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-size: large;">...Houston, we have a Problem!</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; So, let's just Google "UV f-theta" lens and see what we'v....OH MY GOD!!! &nbsp;How much?? F*** it! I'm taking up ballet lessons.</div><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">So, after I drank a cup of water, took a few Xanax pills and did that "Wax on wax off" move, I decided that I had to go back to the initial gantry style of CNC machine.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Note: for those curious enough to ask, a laser printer uses a RED laser. The PLASTIC f-Theta lens in a laser printer is NOT suited at all for the UV laser. The plastic the lens is made of &nbsp;is not transparent to UV light.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-size: large;">...Long story short....</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; So, eventually, &nbsp;after searching the net for all kinds of ways to solve this, I found this site: <a href="http://www.diyouware.com/DiyoPCB-MKI">http://www.diyouware.com/DiyoPCB-MKI</a>&nbsp;and my jaw just dropped. Now, how about that... that was <a href="http://www.diyouware.com/DiyoPCB-MKI" target="_blank">EXACTLY</a> what I wanted to build.</div><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">But first thing's first: let me congratulate the guys (and gals?) over at Diyouware.com for their hard work. Hope to see you in a Kickstarter campaign soon enough.</div><div style="text-align: justify;">And no, I'm not in any way affiliated with them nor am I getting any money from them for writing this.</div><div style="text-align: justify;">So, with the disclaimers out of the way, on with the story...</div><div style="text-align: justify;">&nbsp; &nbsp; &nbsp;I &nbsp;began reading what these fellows did and how they hacked the Blu-ray laser head of the Toshiba drive. Of course, I contacted d the guys, and they recommended me the TwinTeeth variant of the PCB factory. The reason was that the original Mk1 design was kind of clunky and plagued with problems generated by vibrations.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><span style="font-size: large;">Let's get building</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; Now, I have to say, I really appreciate what these guys have done. They did everything from scratch, even developing their own hardware and software platform.&nbsp;</div></div><div style="text-align: justify;"><div style="text-align: justify;">And they've open sourced everything as well. To me, this is awesome, as everyone can get the files and make their own build, modifying it where possible and putting their own spin on things. So guys, a big &nbsp;thumbs up from me!</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">I've decided on building the TwinTeeth Plus version, as this has less 3D printed parts and to me, looks to be more stable mechanical wise.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">First off, I got me some 2 mm thick aluminium sheet (I couldn't find any 3mm plate)<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-WROuDJ6OB2s/WBuWprEcr2I/AAAAAAAACa8/Piy8uloajns55BkFbe_WwsZLr0HHrZ0dwCPcB/s1600/IMAG3345.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-WROuDJ6OB2s/WBuWprEcr2I/AAAAAAAACa8/Piy8uloajns55BkFbe_WwsZLr0HHrZ0dwCPcB/s320/IMAG3345.jpg" width="320" /></a></div><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-dMeaebjYoq8/WBuWpmDr0HI/AAAAAAAACa8/e-zfXol3Zp4FQZCHmoFomkjm6sMaKkGmACPcB/s1600/IMAG3347.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-dMeaebjYoq8/WBuWpmDr0HI/AAAAAAAACa8/e-zfXol3Zp4FQZCHmoFomkjm6sMaKkGmACPcB/s320/IMAG3347.jpg" width="320" /></a></div><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">On these, I glued (OK, scotch taped) the paper templates then marked where the holes would go.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">After this, I went to print the 3 motor holders that the delta sits on. And here is where the real fun begins...</div></div><div style="text-align: justify;"><div style="text-align: justify;">Looking through my collection of stepper motors, I happened to find 3 identical NEMA23 steppers.&nbsp;</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp;The original TwinTeeth &nbsp;needed NEMA17....Yes, this is one of the advantages of having a mechanical engineer for a girlfriend (Thank you!) She helped me modify the motor holder .STL file, so that it took the NEMA23 motors.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-ael7BeRf2h8/WBuWpvU28_I/AAAAAAAACa8/Y9OY-wHW-ck-RN0j7JeG5imly845CVpFwCPcB/s1600/IMAG3350.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-ael7BeRf2h8/WBuWpvU28_I/AAAAAAAACa8/Y9OY-wHW-ck-RN0j7JeG5imly845CVpFwCPcB/s320/IMAG3350.jpg" width="320" /></a></div><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Next up were the bottom lead screw supports. Some F6900ZZ flanged bearings were supposed to be fitted into them.&nbsp;</div><div style="text-align: justify;">Because these bearings seemed to proliferate in the wild planes of eBay, but nowhere near my country and because I got burned by the national postal service (which sucks) too many times,I decided I would replace the flanged bearings for "normal" ones. (flanged bearing was d=10 mm, D=22 mm, 6 mm width; replacement bearing is d=10 mm, D=26 mm, 8 mm width)</div><div style="text-align: justify;">&nbsp;This meant firing up Solidworks and doing my magic. (I was stubborn enough that I wanted to do the part from scratch, by myself - what better way of learning Solidworks)<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-lNn0V1nGRa4/WBuWpuqLToI/AAAAAAAACa8/FatmO8-AEMorcg-KKH6Wx0x3H16dXotNgCPcB/s1600/IMAG3355.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-lNn0V1nGRa4/WBuWpuqLToI/AAAAAAAACa8/FatmO8-AEMorcg-KKH6Wx0x3H16dXotNgCPcB/s320/IMAG3355.jpg" width="320" /></a></div><br /><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Unfortunately, the original dimensions in the .STL files have some wacky values, which proved to be a real pain to replicate. I had to build my own geometry on top of the .STL par to get the dimensions I needed. Then replicated and adapted that so &nbsp;a 6000ZZ series bearing would fit.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Next, I got hold of some 20mm x 20mm square aluminium profile for the legs, 3x10mm, 200mm long &nbsp;ACME (AKA trapezoidal) screws which I ordered to be milled on one end to 8mm, so it would fit in a 6.35mm x 8mm flexible coupling and &nbsp;6 x 6mm, 300mm long guide rails, which I ordered to have M4 bolt holes drilled and tapped into them, at each end.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://3.bp.blogspot.com/-RP3x8dZpqi4/WBuWprphjyI/AAAAAAAACa8/lUUHQDQ4R48OrXgQ6Dgj6fNgZWAZwm2bQCPcB/s1600/IMAG3353.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://3.bp.blogspot.com/-RP3x8dZpqi4/WBuWprphjyI/AAAAAAAACa8/lUUHQDQ4R48OrXgQ6Dgj6fNgZWAZwm2bQCPcB/s320/IMAG3353.jpg" width="213" /></a></div><br /></div><div style="text-align: justify;"><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-EpHuA14Fnhg/WBuWpr_OR6I/AAAAAAAACa8/bKnkjYZgPQgKxU60fkD4MDCpev0fO_9nQCPcB/s1600/IMAG3334.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://1.bp.blogspot.com/-EpHuA14Fnhg/WBuWpr_OR6I/AAAAAAAACa8/bKnkjYZgPQgKxU60fkD4MDCpev0fO_9nQCPcB/s320/IMAG3334.jpg" width="320" /></a></div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-89XHim86nx0/WBuWphTrWBI/AAAAAAAACa8/C0PiR1Zel90KVee6GQF3PDn19EE-MJAvwCPcB/s1600/IMAG3337.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-89XHim86nx0/WBuWphTrWBI/AAAAAAAACa8/C0PiR1Zel90KVee6GQF3PDn19EE-MJAvwCPcB/s320/IMAG3337.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://4.bp.blogspot.com/-7OTjuB1aXaw/WBuWppbNChI/AAAAAAAACa8/5EnyYO7AOX0D9U5EWmP007mLsvrrStZ0QCPcB/s1600/IMAG3339.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://4.bp.blogspot.com/-7OTjuB1aXaw/WBuWppbNChI/AAAAAAAACa8/5EnyYO7AOX0D9U5EWmP007mLsvrrStZ0QCPcB/s320/IMAG3339.jpg" width="320" /></a></div><br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-bkqii41QgW8/WBuW4NjSJXI/AAAAAAAACa8/BHX2i_y-xzsV6U6T27Kqm1J3aMe-HmenACPcB/s1600/IMAG3293.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-bkqii41QgW8/WBuW4NjSJXI/AAAAAAAACa8/BHX2i_y-xzsV6U6T27Kqm1J3aMe-HmenACPcB/s320/IMAG3293.jpg" width="213" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-CcqtSn4UUN0/WBuW4IWSFxI/AAAAAAAACa8/SoXg1axkEyo_kyELiThmTKK1z9OwEKqFACPcB/s1600/IMAG3294.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-CcqtSn4UUN0/WBuW4IWSFxI/AAAAAAAACa8/SoXg1axkEyo_kyELiThmTKK1z9OwEKqFACPcB/s320/IMAG3294.jpg" width="213" /></a></div><br />I also got some extra help for this build<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://2.bp.blogspot.com/-mIr80yVRR4c/WBuWprdgGNI/AAAAAAAACa8/dIaelxrXIQ03cNMsXFM-eQjhngKQ7Of_gCPcB/s1600/IMAG3352.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-mIr80yVRR4c/WBuWprdgGNI/AAAAAAAACa8/dIaelxrXIQ03cNMsXFM-eQjhngKQ7Of_gCPcB/s320/IMAG3352.jpg" width="320" /></a></div><br />He knows the vernier scale can be tough to read sometimes, so any help is welcomed.<br /><br />Also, I know, the picture quality is really crappy.... I gotta get me one of those newfangled things called a camera. Tin-type photos, anyone?<br /><br /></div><div style="text-align: justify;"><span style="font-size: large;">Inches, millimeters, mills, centimeters....</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; The only thing I found difficult about this project so far is modifying the existing parts. It's not that they're in .STL format.... it's the fact that the dimensions are kind of all over the shop.</div><div style="text-align: justify;">At least, this is what I gather from measuring the provided .DWG files and the original .STL models. I mean, there are hardly any measurements that seem to have nice round values. I don't know if this is due to the fact that the design was done in inches, then converted to mm, or something else is going on, but it makes things kind of hard when it comes to taking measurements.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;">...come one, come all....</span></div><div style="text-align: justify;"><span style="font-size: large;"><br /></span></div><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp;This is the link to the <a href="https://github.com/catt87/TwinTeeth" target="_blank">GitHub page</a> that contains the modified files. Like I said, I used NEMA23 steppers and &nbsp;6000ZZ bearings and some of the 3D prints were modified for &nbsp;MY specific build.</div><div style="text-align: justify;">&nbsp; As the build will continue, I will modify other parts as well. Why? Because it's interesting and because I have &nbsp;an OCD about improving stuff.<br />Next will probably be the ACME nut for the 10 mm screws. I don't know if &nbsp;a bough ACME nut will have more or less backlash than the original TwinTeeth method, where a mold of the screw was made and used as a nut, but those linear bearings held to the mount with &nbsp;zip-ties...kinda make my skin crawl.&nbsp;</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-80752125572786226202016-10-09T19:33:00.001+03:002016-10-14T16:11:18.891+03:00EF Johnson 242-5876 2-Way Radio Teardown<div class="separator" style="clear: both; text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; Well, this teardown has been in the making for some time now. I'm not particularly big on RF stuff, but I had a hunch that this thing would be nicely engineered and built on the inside. I was expecting a lot of analog goodness mixed with some digital control.</div><div class="separator" style="clear: both; text-align: justify;">And what do you know.....I was right.</div><div class="separator" style="clear: both; text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <a href="https://1.bp.blogspot.com/-EGR69l-rRfs/V88PvlWD_eI/AAAAAAAACIE/opPW8wonW-MSX4KKW9sziGoWBRLqNewIwCPcB/s1600/IMAG3012.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://1.bp.blogspot.com/-EGR69l-rRfs/V88PvlWD_eI/AAAAAAAACIE/opPW8wonW-MSX4KKW9sziGoWBRLqNewIwCPcB/s400/IMAG3012.jpg" width="265" /></a></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; Now, I've searched high and low for a manual to this thing, but I wasn't able to find anything. And when I say "anything" I mean absolutely nothing relating to that model number, which kind of lead me to believe that these things (of which I have two in my possession) might be a custom &nbsp;police or military issue (police most likely).</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp;If anyone has a user manual, or better yet, a service manual, please leave a comment. I'd really like to see how this thing ticks.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Most of the hand-held stuff I came across from EF Johnson seems to be operating on the 800-900 MHz range, but this thing &nbsp;seems to work on the 80-100 MHz range. I did a quick FFT on my Rigol 1054 and there seems to be a nice big spike at about 88 MHz when I press the transmit button. Also, the FM receiver chip is spec'd for up to 200 MHz.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">However, this should be taken with a grain of salt, because these things require a network infrastructure to work. So without that network, I can't say for sure that that spike I see isn't just a signalling band or something.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Ok, enough talk. Let's get into the meat of it.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;<a href="https://2.bp.blogspot.com/-PmTw4DXgXTI/V88PvqusofI/AAAAAAAACIU/lX4WhJ09oBw7MF6X_vL-zEaoF_ZKf2JowCPcB/s1600/IMAG3021.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-PmTw4DXgXTI/V88PvqusofI/AAAAAAAACIU/lX4WhJ09oBw7MF6X_vL-zEaoF_ZKf2JowCPcB/s320/IMAG3021.jpg" width="213" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">This thing is ancient. How I know this? It uses Ni-Cd Batteries. 7.5V, 1.4 Ah. And yes, they still take a charge, but that might be because at some point in time someone sawed off the back of the battery pack and stuck new batteries in it.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <a href="https://1.bp.blogspot.com/-vc3a9hhYYXs/V88Pvg6pW2I/AAAAAAAACIE/04yDM7Sj23Ehbp8xAkC2Y-DuR9ONcjK0ACPcB/s1600/IMAG3025.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-vc3a9hhYYXs/V88Pvg6pW2I/AAAAAAAACIE/04yDM7Sj23Ehbp8xAkC2Y-DuR9ONcjK0ACPcB/s320/IMAG3025.jpg" width="213" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Taking the back off, you can immediately see this thing resembles something that's MIL-spec. A nice thin cast magnesium (probably) shielding with a ton of screws.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="https://2.bp.blogspot.com/-dsmZ1M8tZ-c/V88Pvrj_CaI/AAAAAAAACIE/xRaHgtStIbUSECaLT4i69Z3aZ81OXKtwACPcB/s1600/IMAG3029.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://2.bp.blogspot.com/-dsmZ1M8tZ-c/V88Pvrj_CaI/AAAAAAAACIE/xRaHgtStIbUSECaLT4i69Z3aZ81OXKtwACPcB/s400/IMAG3029.jpg" width="400" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Lifting up &nbsp;the skirt, this thing really looks packed full of parts. (Yes, I know, I have to get a better camera.)</div></div><div style="text-align: justify;"><div style="text-align: justify;">The two 14 pin chips are a Motorola <a href="http://www.onsemi.com/pub_link/Collateral/MC14066B-D.PDF" target="_blank">MC14066B </a>Quad Analog Switch (the one on the left) and a <a href="http://www.onsemi.com/pub_link/Collateral/MC14094B-D.PDF" target="_blank">MC14094B </a>8 stage shift register with 3-state outputs.</div></div><div style="text-align: justify;"><div style="text-align: justify;">The smaller 8 pin one is an <a href="http://pdf1.alldatasheet.com/datasheet-pdf/view/130546/MOTOROLA/MC939.html" target="_blank">MC939 &nbsp;</a>divide by 6 counter (I think...)</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;<a href="https://2.bp.blogspot.com/-D_Wr7j-D2IE/V88PvvDdSbI/AAAAAAAACIE/hwayuedkok0Z6_q0mzOhP2spHlRxLWWgwCPcB/s1600/IMAG3035.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://2.bp.blogspot.com/-D_Wr7j-D2IE/V88PvvDdSbI/AAAAAAAACIE/hwayuedkok0Z6_q0mzOhP2spHlRxLWWgwCPcB/s320/IMAG3035.jpg" width="213" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">The face together with the keypad came right off, revealing another shield, also cast magnesium, together with a boatload of adjustment pots and caps.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;<a href="https://2.bp.blogspot.com/-c9QahCQrkC8/V88Pvp2SREI/AAAAAAAACIE/Jwedmj6jJbgzyZSBmjQy5jdAnC5z6fFtQCPcB/s1600/IMAG3040.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://2.bp.blogspot.com/-c9QahCQrkC8/V88Pvp2SREI/AAAAAAAACIE/Jwedmj6jJbgzyZSBmjQy5jdAnC5z6fFtQCPcB/s320/IMAG3040.jpg" width="320" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">On the back of the face, there are two boards stacked together and which connect to the rest of the unit only through that pin header. Also, notice the nice o-ring&nbsp;&nbsp;seal&nbsp;(OK, not really O-shaped, but you get the picture). A bit of it is peaking out in the lower left corner.</div></div><div style="text-align: justify;"><div style="text-align: justify;">There are a few goodies on these boards, but let's leave it to the side for now and take a look at what;s under that other shield.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="https://3.bp.blogspot.com/-K_qard9z10Y/V-402uV9GCI/AAAAAAAACJo/SpSKtIspEMk338QTAzhcBgb5SZRlMMqBwCPcB/s1600/IMAG3051_edited.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://3.bp.blogspot.com/-K_qard9z10Y/V-402uV9GCI/AAAAAAAACJo/SpSKtIspEMk338QTAzhcBgb5SZRlMMqBwCPcB/s320/IMAG3051_edited.jpg" width="320" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Et Voila! This is the good stuff. A whole myriad of analog and digital goodness, just waiting to be reverse-engineered. Not by me, mind you. I'm not into this kind of stuff, remember?</div></div><div style="text-align: justify;"><div style="text-align: justify;">And, because I have a shitty camera, I tried to make things easier, hence the red markings.</div></div><div style="text-align: justify;"><div style="text-align: justify;">So. from the top left corner, we have the <a href="http://pdf.datasheetcatalog.com/datasheet/motorola/MC3362DW.pdf" target="_blank">MC3362DW </a>&nbsp;FM receiver chip. Now the datasheet says it works up to 200 MHz, and this is consistent with what I saw on my scope's FFT.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">On the right, we have the <a href="http://www.changpuak.ch/electronics/datasheets/MC145151-2.pdf" target="_blank">MC145158-2</a>&nbsp;which is a serial input PLL sinthesizer. &nbsp;The two&nbsp;<a href="https://www.nxp.com/documents/data_sheet/PCF8574.pdf" target="_blank">&nbsp;PCF8574</a>&nbsp; probably shift data to and from the two vertical boards. Unfortunately, I couldn't read the part numbers &nbsp;off the ICs because there was no angle I found that allowed me to do so.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">What I plan to do &nbsp;is if and when I get a hold of some manuals for this specific model, I'll &nbsp;do another teardown sometime and desolder these 2 boards and have a proper look at what's happening in here. Also, I want to poke around some stuff in there with the ol' 1054 scope. Some LO's, some I2C buses... stuff like that. Who knows, maybe I'll even get to learn more about the RF side of things.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Ok, so now let's get back to the boards on the faceplate.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;<a href="https://3.bp.blogspot.com/-_kXOGA9GWAY/V88PvhXAK7I/AAAAAAAACIE/Dj9tJn63wBIhpzIR43X6JEixqlyS91H9wCPcB/s1600/IMAG3065.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://3.bp.blogspot.com/-_kXOGA9GWAY/V88PvhXAK7I/AAAAAAAACIE/Dj9tJn63wBIhpzIR43X6JEixqlyS91H9wCPcB/s400/IMAG3065.jpg" width="400" /></a></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">&nbsp; &nbsp; &nbsp;So, first thing to notice is the big chip to the left of the speaker. That's the&nbsp;<a href="http://pdf1.alldatasheet.com/datasheet-pdf/view/18216/PHILIPS/PCF8576T.html" target="_blank">PCF8576T</a>&nbsp;driving the LCD on the front. And, of course, it's controlled via I2C. To the left of that, there is a keyboard &nbsp;controller, the <a href="http://www.ti.com/lit/ds/symlink/mm54c923.pdf" target="_blank">MM74C923</a>. It can encode up to 20 keys, which is &nbsp;5 more than what the faceplate has. "What a waste" I hear you say?</div></div><div style="text-align: justify;"><div style="text-align: justify;">Well, yeah, but being the smart engineers that they are, they probably read the datasheet and it looks like if you're decoding a 5 by 4 button matrix, then the 923 is the way to go.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Here's a funny thought....maybe a Rigol engineer will somehow make his/her (everybody deserves to be an engineer) way to this blog and decide to turn over a new leaf and actually start reading some datasheets. They're free to download, people... just so you know.</div></div><div style="text-align: justify;"><div style="text-align: justify;">OK, rant over.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Just above the 923 controller, there's a 14-pin <a href="http://www.tv-sputnik.com/x24c16.pdf" target="_blank">X24C16</a>&nbsp; 16Kbit (2048x8) EEPROM, with an I2C interface, as one would expect. Chalking this one also on the list to probe, for the next teardown.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Now, going to the other board, we have the big chip to the left. It's made by Motorola, just like &nbsp;most of the other chips in these units, except my Google-Fu can't come up with a part number. Most likely it's a custom part...hence the label on it.<br /><br />Also, the buttons on the side &nbsp;seem to match the ruggedness of the unit. Despite how mucky the bottom transmit button looks, it's still got some life in it....as long as you press it juuust right. It's one of those Goldylocks things. not too hard, not too light of a press....<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-KxGMGvXhXV4/V88Pvup3rKI/AAAAAAAACIE/qdEi6yczTdgDVOzVVzLR7hZdAkXE4jkWgCPcB/s1600/IMAG3073.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://1.bp.blogspot.com/-KxGMGvXhXV4/V88Pvup3rKI/AAAAAAAACIE/qdEi6yczTdgDVOzVVzLR7hZdAkXE4jkWgCPcB/s400/IMAG3073.jpg" width="266" /></a></div><br /><br />And, after putting it all together again, what do you know....It still works<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-aqgSWvfWhG0/V88PvuL_NII/AAAAAAAACIE/xQPhlwKERmYeswDwlAGmlBGlx3bCWNJxwCPcB/s1600/IMAG3074.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://1.bp.blogspot.com/-aqgSWvfWhG0/V88PvuL_NII/AAAAAAAACIE/xQPhlwKERmYeswDwlAGmlBGlx3bCWNJxwCPcB/s320/IMAG3074.jpg" width="213" /></a></div><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">All in all. I'm pretty impressed how this thing was built. You gotta love the good ol' days.&nbsp;</div><div style="text-align: justify;">If and when I get hold of some more information about this radio, Ill try and play around with it a bit more, maybe even connect it up to a PC and see if I can modify something in the firmware.&nbsp;</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><a href="http://www.repeater-builder.com/johnson/pdfs/efj-rpi.pdf" target="_blank">This link</a> has some info on how the remote interface cable and about the PC software.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">I'm also going to do a mini-teardown of the charger, just to see what's in there. I have 2 kinds of chargers: one that plugs in directly into an AC outlet and another that takes in 18 V DC, so stay tuned for that as well.</div><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;">Full <a href="https://goo.gl/photos/PHT27WQFzaYGB6X59" target="_blank">teardown pictures</a> are available on my <strike>Picasa</strike>&nbsp;Google Photos page.</div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div><div style="text-align: justify;"><div style="text-align: justify;"><br /></div></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-44917011357432613562016-01-14T21:01:00.001+02:002016-12-21T16:33:55.478+02:00Picoscope 3000 Series Review....or maybe not<div style="text-align: justify;">&nbsp; First off, let me start by saying that this is not really&nbsp; a full review, but more accurately a first impression after I got to play around with one of these things.&nbsp;</div><div style="text-align: justify;">And because it's a PC scope, the impressions are not so much about the physical aspect of the scope as it is about it's user interface. And, boy, do I have some comments to make here...</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;">"High Performance USB Bla bla bla...."</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; The culprit....sorry, I mean the product I had the... opportunity? to play with is a Picoscope 3406D MSO PC oscilloscope.</div><div style="text-align: justify;">This little thriller comes with 4 analog channels and 16 digital channels, a 1 GS/s real time sampling (even though the software lets you select all the way up to 2GS/s, but I don't know if that really does anything or it's there just for&nbsp; the fun of it), USB 3.0 and more features than you can poke a stick at.</div><div style="text-align: justify;">Yeah, right.&nbsp;</div><div style="text-align: justify;">And let me make an analogy here: suppose you go to the&nbsp; local car dealership and go around the show floor, only looking at the specs where it says "Horsepower", paying absolutely no attention to, let's say, how comfortable the interior of the car is, or how well it drives on the street, or... I think you get the point.&nbsp;</div><div style="text-align: justify;">When you do find the one with the most horsepower, you give the dealer all you hard earned money, two small coins, a bottle cap and a paperclip you happen to have in your pocket, making sure you quickly but the latter two back in you pocket, as fast as discretely as possible.</div><div style="text-align: justify;">After&nbsp; you drive home, happy about you new purchase, you will be hit by the worse case of buyer's remorse, ever, because, you will have realized that you just bought the most ugly, uncomfortable, unusable car in history. See where I'm going with this?</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, yes, the hardware specs for the Picoscope 3000 series are very nice, and maybe the scope would deliver on them.....who knows... because I was too preoccupied with getting the software interface of&nbsp; this thing to actually&nbsp; work and with scouring through the menus to find basic stuff&nbsp; like a cursor,&nbsp; getting the waveforms to actually fit in the center of the screen, and so on. And for these kinds of scope, where all you have is the interface to it, no buttons or knobs, how it looks and feels makes all the difference.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Yes folks, it's bad. The Picoscope software interface is horrific. In the year 2016, when more and more really nice PC scopes are coming on the market, the interface is really frustrating and awkward to use. This, combined with the fact that it looks like something from 10 years ago, really makes you wonder why on earth someone would go and buy this product, as opposed to any other scope of the same caliber.&nbsp;</div><div style="text-align: justify;">First of all, when you start the application, as a first time user you will be met by the most mild-mannered and spartan GUI yet. Also, notice the selected 2 GS/s rate. YEAH baby, now we're talking&nbsp; </div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;"><a href="http://4.bp.blogspot.com/-tjFvCN7mP68/VpfcY03svTI/AAAAAAAABVc/IXRi7hZxucY/s1600/Picoscope_2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="346" src="https://4.bp.blogspot.com/-tjFvCN7mP68/VpfcY03svTI/AAAAAAAABVc/IXRi7hZxucY/s640/Picoscope_2.jpg" width="640" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">At first glance, you'll notice that it has all the things a normal scope should have....like time-base and Volts/div settings...and trigger settings. Sweet!</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;">On to the fun stuff</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Now, for any engineer that has ever used a scope for more than 5 minutes, you will soon realize that for some measurements, you need some way to measure the time interval between event A and event B in time. Nothing more simple, just press the "Cursor" button an a scope's front end. <!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument></xml><![endif]--></div><div style="text-align: justify;"><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles></xml><![endif]--><!--[if gte mso 10]><style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style><![endif]--> </div>Well, this detail seems to have escaped the guys that designed this interface. After a frustrating hour of searching all the menus, all the nooks and crannies this interface has and calling another one of my colleagues to the rescue, nu luck. No "Cursor" tab, or menu, or anything like that. Only a daft looking green&nbsp; little circle tucked away in the lower right corner, that has the amazing property of displaying "0°" on it, no matter where you move it on the waveform. <br /><br />Again, this is from the perspective of a first time user. It shouldn't be rocket science to use one of these devices and I do apologize if some people that have read the user manual for the GUI know where everything is, that still does not make it any easier to operate. <br /><br />This thing is also boasting all kind of communication protocols decoding, which is very handy. Except that, with 4 analog channels and 6 digital lines, all 6 with CAN protocol decoding on them, the GUI gets sluggish sometimes. And that happened on a i7 core machine with about 8 Gigs of RAM on it.<br />Also, that "real time sampling" thing....in the scenario I used it, no way was that real time. But who am I to complain.<br />Also, there was a very peculiar thing I stumbled upon....the traces would not zero properly, i.e. they had a a butt load of offset, one of them about 100 V. But, the guys from Picoscope thought of this ahead, and put in an auto-zeroing button for each channel<br /><br /><div class="separator" style="clear: both;"><a href="http://2.bp.blogspot.com/-ECOFZ8N0Asw/Vpfr8mPsrWI/AAAAAAAABVs/bg-Vh4i07iY/s1600/Picoscope_2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://2.bp.blogspot.com/-ECOFZ8N0Asw/Vpfr8mPsrWI/AAAAAAAABVs/bg-Vh4i07iY/s640/Picoscope_2.jpg" width="640" /></a></div><br /><br />Too bad each time I zeroed channels B, C or D, the application crashed. <br />&nbsp;A nice thing is that this thing always has the last 32 frames on hand, so you can review them&nbsp; at any time, to see any missed signal behavior (see the "32 of 32" in the upper middle of the photo). Nice feature this is. But unfortunately, from all the button pushing, my application decided to go all Alzheimer on me and by the time I managed to set up my signal capture profile, both analog and digital (it only took abut 2 or 3 hours, what would have taken me 1 minute on any other mixed signal scope), the GUI only had the current frame on memory, and nowhere could I find something referring to the buffer size or history or the like. So, yeah, all we had to go on was a trigger on a certain event an hoped that all went well.<br /><br /><span style="font-size: large;">The Bottom Line</span><br /><br />If this software was a pre-beta, OK, I would excuse a few mistakes in the code, here and there. But it's not. The version I downloaded was the latest one. It even said "stable" in the comments next to the version name, in Picoscope's Downloads page, so it had to be good. (F.Y.I. This version also crashed when I hit the "Zero" button for channels B C or D)<br /><br /><div class="separator" style="clear: both;"><a href="http://4.bp.blogspot.com/-XNIw3BIXXgU/VpfXPixMt8I/AAAAAAAABVM/IHphgLFGwss/s1600/Picoscope_1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="332" src="https://4.bp.blogspot.com/-XNIw3BIXXgU/VpfXPixMt8I/AAAAAAAABVM/IHphgLFGwss/s640/Picoscope_1.jpg" width="640" /></a></div><br /><br />&nbsp;I wonder why the latest version didn't work......<br /><br />Anyway, a LOT of improvement is necessary here. The guys at Picoscope need to step up their game and actually build a GUI that works. I'll even lend them my scope and see how that works, since obviously none of them ever touched a scope before, otherwise they would have known to put all the common and important stuff where it can easily be accessed, front and center.<br /><br /><span style="font-size: large;">So, what's next?</span><br /><br />Well, I've been doing a lot of work an my own personal projects lately, and built some nice gear. Of course I'm going to share them, pictures, schematics and all. Also, there's some power supply stuff going on that I want to share.<br /><br />Also, I've been thinking about building my own LCR meter. After reading and doing some hard core research on the matter, I came up with a configuration&nbsp; that I hope will work.<br /><br />So, more interesting design posts to come.<br /><br />Have fun and keep playing<br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument></xml><![endif]--><br /><br /><div style="text-align: justify;"><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles></xml><![endif]--><!--[if gte mso 10]><style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style><![endif]--> <!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument></xml><![endif]--></div><div style="text-align: justify;"><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles></xml><![endif]--><!--[if gte mso 10]><style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style><![endif]--><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com1tag:blogger.com,1999:blog-6412238293976072298.post-87127147049951651322015-10-27T20:45:00.000+02:002017-07-27T20:31:06.159+03:00High Voltage Differential Probe Design and Build - Part 1<div style="text-align: justify;"><br />This project will be made of multiple parts. First, I'll explain the basics of designing a differential probe then the following posts will be about how to actually do the math and lay out the PCB for something like this.<br />But first thing's first:<br /><span style="font-size: large;"><br /></span><span style="font-size: large;">"Excuse me, how much is this?"</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Have you ever &nbsp;wondered why are differential oscilloscope probes so expensive? Well, I have, and the answer is....out there?!</div><div style="text-align: justify;">No, seriously, I would accept a price of 100 to 150 Euros for a probe, maybe even 200 Euros, but anything over this seems like &nbsp;a waste of money, considering what these devices have inside them (we'll get into this a bit later). Also, some manufacturers just re-brand&nbsp; probes as their own and add an extra 50-100 Euros just because it has some fancy well known T.E. manufacturer logo on it.</div><div style="text-align: justify;">Lately, the prices on eBay have jumped to some ludicrous amounts just because the sellers think they have the market cornered. Of course. they're just being stupid.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;">So, WHAT are these things made of?</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp;For starters, an input attenuation stage which is nothing more than a compensated resistive divider (one divider for the positive and negative input) followed by a differential amplifier. Simple, right?. The input attenuation stage is designed either with two high voltage resistors and two caps in parallel, or multiple lower voltage rated resistors.</div><div style="text-align: justify;">After the input signal has been divided down to a reasonable level, a differential stage comes next. This rejects the common mode noise and does some amplification, if needed, then this passes it on to the next stage, where differential to single-ended conversion takes place.</div><div style="text-align: justify;">This will be the actual signal that your oscilloscope sees. Follow this by an optional&nbsp; output stage, if you need that 50 Ohms matching impedance, and that's all.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">It may sound complicated, but there's really nothing to it. You could build one for 30 or 40 Euros, designed either for high voltage (1KV to 2KV) and low bandwidth (about 20 MHz) or lower voltage but higher bandwidth (up to 1GHz). For the latter, the design shown here : <a href="https://xellers.wordpress.com/electronics/1ghz-active-differential-probe/">https://xellers.wordpress.com/electronics/1ghz-active-differential-probe/</a> is relatively simple, inexpensive and very useful. It'll go up to 1Ghz bandwidth and -20dB attenuation which is all most people ever need in their prjects.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">I wanted, as an exercise, to design and build a high voltage probe, capable of taking in a differential signal of up to 1.5 KV and with a bandwidth of somewhere around 15-20 MHz. Also it must have variable attenuation (1/10 and 1/100 or 1/50 and 1/500) and be powered from a 9 Volt battery - this last part is to make sure there isn't going to be any ground loops that can ruin your day and also it makes shielding the whole circuit much easier. Most importantly, it should cost below 50 Euros in parts (does not include the PCB, if I decided to have one made and not go DIY on this).</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">For starters, I took an already existing design&nbsp; then replicate that so to keep the costs down. &nbsp;K.I.S.S. right?</div><div style="text-align: justify;">I searched for a schematic (easier said than done) of an existing commercial &nbsp;differential probe then took that as a scaffolding for my design.</div><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; I managed to track down a schematic on this site:&nbsp;<a href="http://www.diyaudio.com/forums/equipment-tools/248505-differential-probe-reverese-engineered.html">http://www.diyaudio.com/forums/equipment-tools/248505-differential-probe-reverese-engineered.html</a>&nbsp; which together with with the teardown pictures from <a href="http://bardagjy.com/?p=1664">here</a>, gave me a pretty good idea of how to go about building the probe.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">For anyone trying to do the same, or just and make sense of the schematics from the above link, some values for components are not the right ones. I got some values by cross-referencing the schematic to the actual photos of the probe. What values I could't find at all, I calculated them or mucked around in LT Spice until I got a satisfactory response from the circuit.</div><div style="text-align: justify;">This is my first project where I'm working with frequencies above 1 MHz, so bare with me here.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;">"So I want to build a High Voltage differential probe. Ho do I do this?"</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;"><span style="font-size: small;">&nbsp; &nbsp; This is where the real magic happens. Once I had the general idea behind these probes, I got down to the nitty-gritty. Although the input stage is the first one an input signal sees, I started off with the differential amplifier.</span></span></div><div style="text-align: justify;"><span style="font-size: large;"><span style="font-size: small;">The schematics in the previous links don't make much sense, so let me put things into perspective:</span></span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-ul81Y_hglVU/VhO0B7m4VxI/AAAAAAAABSg/Kua_vc5zoTs/s1600/Untwwwwwwitled.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="537" src="https://4.bp.blogspot.com/-ul81Y_hglVU/VhO0B7m4VxI/AAAAAAAABSg/Kua_vc5zoTs/s640/Untwwwwwwitled.jpg" width="640" /></a></div>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Please see the later edit below for an update for this schematic</div><div class="separator" style="clear: both; text-align: center;"><span style="font-size: large;"><span style="font-size: small;"><a href="https://www.blogger.com/blogger.g?blogID=6412238293976072298" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a></span></span></div><br /><div style="text-align: justify;"><span style="font-size: small;">&nbsp; &nbsp; Looks friendlier now, doesn't it? Now let's see how this thing works. It's basically just a JFET differential amplifier with some bits stuck to it to make the thing behave better from DC all the way to&nbsp; a couple of MHz. The guts of this thing is the matched JFET pair Q4A and Q4B. For&nbsp; those who are just getting to grips with electronics, matched means that both of these transistors are housed in the same package so as the noise and temperature affects them in the same manner and you don't get an imbalance in the amplifier.</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: small;">&nbsp; &nbsp; "So, why don't I just stick the output from the input attenuation stage into an op-am&nbsp; instead of reading this long post? "</span></div><div style="text-align: justify;"><span style="font-size: small;">Well, I'm glad you asked. Thing is, you want a very high impedance at the input of this probe. Sure, you might have a few resistors of a couple of MegaOhms on the input, isn't that enough? Nope, The more the better. But the bigger the input impedance, the bigger the gain-setting resistors will have to be. And those values, together of the capacitance of the input of your op-amp will make a low pass filter which will slow down the op-amp itself. And when you want to go into the 10-20 MHz region, that just won't cut it.</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: small;">&nbsp; &nbsp; "Then, how about we buffer the input with a few more op-amps?"</span></div><div style="text-align: justify;"><span style="font-size: small;">Yes...and No. You could, but you'd need some high speed op-amps, to form an "instrumentation amplifier" design:</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: small;"><img alt="https://xellers.files.wordpress.com/2014/03/simple-differential-amplifier.png" class="decoded" height="337" src="https://xellers.files.wordpress.com/2014/03/simple-differential-amplifier.png" width="640" />&nbsp; </span></div><div style="text-align: justify;"><span style="font-size: small;">&nbsp; &nbsp; But high speed op-amps are expensive. Also you don't just stick the output of an op-amp into the input of another at high frequencies, because they tend to oscillate and do all kinds of other unpleasant things.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: small;">OK, if you actually go and try this with three op-amps that have a bandwidth of, say, 200 to 500 MHz (I'm talking about the Gain-Bandwidth Product here), odds are it will do the business.&nbsp;</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: small;">&nbsp; &nbsp; But there is another factor to take into consideration. Common Mode Rejection. Remember that you'll be measuring differential voltages with this probe. Meaning, you can stick the negative terminal of the probe anywhere in the circuit and measure THAT relative to the Positive one. But that Negative terminal can sometimes be at a potential that is not Ground. It can be at a potential of +150 Volts and the Positive at +300 Volts. So you'll be measuring +150 Volts, but that signal will be piggy-backing on top of another 150 volts from ground, which your probe will have to ignore.&nbsp;</span></div><div style="text-align: justify;"><span style="font-size: small;">How does it do that? With a high Common Mode Rejection Ratio (CMRR).</span></div><div style="text-align: justify;"><span style="font-size: small;">The three op-amps previously talked about will most likely work, but the&nbsp; low CMRR of the design will let you only measure voltages that are near Ground potential. (a few tens of volts, maybe a hundred or two, depends on your choice of op-amp). Most op-amps tend to have a CMRR that drops the further up in frequency and gain you go.</span></div><div style="text-align: justify;"><span style="font-size: small;"><br /></span><span style="font-size: small;">&nbsp; &nbsp; Sorry for the long detour, but this was needed to explain the whole idea why a JFET differential input should be used (at least in my case).</span></div><div style="text-align: justify;"><span style="font-size: small;">Now back to the story.&nbsp;</span></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: small;">&nbsp; &nbsp; "So, we're going to be using the JFETs. What do the rest of the things in the circuit ACTUALLY do?"</span></div><div style="text-align: justify;"><span style="font-size: small;">&nbsp;</span>&nbsp; Another fine question. So, starting from the top, R13 and R24 are drain resistors that set the gain of our differential stage. The gain will be G = gm*R<span style="font-size: xx-small;">D</span> <span style="font-size: small;">where </span>gm is the transconductance of the JFETs and R<span style="font-size: xx-small;">D <span style="font-size: small;">is the value of R13 = R24 (the drain resistors).</span></span></div><div style="text-align: justify;"><span style="font-size: xx-small;"><span style="font-size: small;">Now, because JFETs usually have a very low transconductance, that means that the gain will be relatively small. No big deal you say? Well, remember the probe will be a selectable 1/10 and 1/100 one, so at some point, you will need to step up the gain so you can measure small signals (tens of volts), not just whopping big Kilo-volt signals.</span></span></div><div style="text-align: justify;"><span style="font-size: xx-small;"><span style="font-size: small;">To step up the gain, you could just increase the Drain resistors, but that will limit the current through the JFETs. Also, you can't whack in just any resistors. Resistors have a tolerance rating and also a temperature coefficient. Because the JFET pair is matched, you'll need matching drain resistors also. "Matched" meaning they'll have to behave the same, so 1% or better tolerance resistors are needed and a temperature coefficient as low as possible is also a must (50ppm or less). But that means more money.</span></span></div><div style="text-align: justify;"><span style="font-size: xx-small;"><span style="font-size: small;">So another trick would be to increase the transconductance of the FETs and that's what&nbsp; Q5B-R17 and Q5C-R35 are doing. </span></span><br />Their role is twofold: first, they provide a somewhat constant current (they sink current) of V<span style="font-size: xx-small;">BE</span>/R<span style="font-size: xx-small;">B </span>and second, they provide a low impedance output. The Base resistors will have to be well matched and also their value set for the particular FET one might use i.e. match the current sink to the value of &nbsp;I<span style="font-size: xx-small;">DSS</span>.&nbsp; And even so, in some cases, the drain current will still vary with temperature, so I'll have to see if I leave things as they are now.<br />&nbsp;So, let's say that each leg of the differential amp sinks a current of 2 mA (that's 1mA for the Q4A/B and 1mA for &nbsp;Q5B/C), that means the current sink in the tail of the differential amplifier will sink a total of 4mA. Q5 Q6 amd Q7 make up a Wilson current mirror, with the current established by Q8. Diode D1 is actually a LED which will provide the base current for &nbsp;Q8.<br /><br />&nbsp; &nbsp; Now, of course, this circuit does have some drawbacks, the main one being the power supply voltage. For example, if the whole thing will be powered directly from some batteries (a 9 volt one maybe), the positive rail will inevitably go down, taking the current through R13/R24 with it. This will cause the whole circuit to go berserk.<br /><br />&nbsp; &nbsp; To resolve this issue, one could swap out the BJTs in the source of the JFETs with PNP transistors, this time connected to the drain. This configuration will give a stable drain current, regardless (within reasonable values of voltage drop, of course) of how much the positive rail sags.<br /><br />&nbsp; &nbsp; I've done some simulations in LT Spice and noticed that the configuration with the NPNs in the Source has a flat &nbsp;bandwidth response to about 22-25 MHz and the one with the PNPs only goes to about 1 MHz or so and also very hard to tweak it to get it to have the right gain AND response.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-laAItnWWwbs/Vi_B7zloPEI/AAAAAAAABTk/h3tBnOfTw6A/s1600/Diff%2BProbe%2Bresponse.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="187" src="https://3.bp.blogspot.com/-laAItnWWwbs/Vi_B7zloPEI/AAAAAAAABTk/h3tBnOfTw6A/s640/Diff%2BProbe%2Bresponse.jpg" width="640" /></a></div>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;This is with the NPN BJTs in the Source of the JFETs<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/--pNnkTEuk9I/Vi_B7_ZguFI/AAAAAAAABTs/LNg2gFjk3-4/s1600/PNP%2Bin%2BDrain.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="184" src="https://4.bp.blogspot.com/--pNnkTEuk9I/Vi_B7_ZguFI/AAAAAAAABTs/LNg2gFjk3-4/s640/PNP%2Bin%2BDrain.jpg" width="640" /></a></div>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;This is with the PNP BJTs in the Drain of the JFETs<br /><br />So, I think I'll go with the configuration that has the NPNs in the Source, just like it is on the commercial probes. It's going to be battery powered, with a DC-DC converter that 's going to give me the&nbsp;+9 and -9 volts rails and hopefully not be bothered pretty much by that positive rail voltage sagging issue.<br /><br /><br />In the next post, I will give some more details about how the circuit behaves in the simulations and show how to choose the right JFETs and other components.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">For anyone interested in this subject and/or those searching for inspiration, the following links may be of some use:</div><div style="text-align: justify;"><br /></div><ul style="text-align: justify;"><li>&nbsp;&nbsp;<a href="http://www.eevblog.com/forum/projects/my-first-project-low-cost-differential-probe/">http://www.eevblog.com/forum/projects/my-first-project-low-cost-differential-probe/</a></li></ul><ul style="text-align: justify;"><li>&nbsp;<a href="http://www.eevblog.com/forum/projects/oshw-diy-1kv-100mhz-differential-probe-(dilemma-vs-hope)/">http://www.eevblog.com/forum/projects/oshw-diy-1kv-100mhz-differential-probe-(dilemma-vs-hope)/</a></li><li><a href="http://www.dgkelectronics.com/high-voltage-differential-probe/">http://www.dgkelectronics.com/high-voltage-differential-probe/</a></li></ul><ul style="text-align: justify;"><li><a href="http://electronics.stackexchange.com/questions/29363/is-this-a-good-design-layout-of-an-active-differential-scope-probe">http://electronics.stackexchange.com/questions/29363/is-this-a-good-design-layout-of-an-active-differential-scope-probe</a></li></ul><div style="text-align: justify;"><b><span style="font-size: x-large;">Later edit:</span></b><br /><b><br /></b>&nbsp; &nbsp; Thank you Marko for spotting my mistake in the initial schematic of the probe. I wanted to redo this for quite some time...looks like this is a good a time as any.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: justify;"><a href="https://4.bp.blogspot.com/-TDlUvbFzYBc/WXoXP9mUghI/AAAAAAAADhs/rKY3jCD8ujkkGXmfaLBc5o4agk2ylmXzwCKgBGAs/s1600/Diff_Probe_Redo.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="708" data-original-width="834" height="540" src="https://4.bp.blogspot.com/-TDlUvbFzYBc/WXoXP9mUghI/AAAAAAAADhs/rKY3jCD8ujkkGXmfaLBc5o4agk2ylmXzwCKgBGAs/s640/Diff_Probe_Redo.jpg" width="640" /></a></div><br /></div><div style="text-align: justify;"><br />&nbsp; &nbsp; The output from the &nbsp;JFET buffer is now taken from the Drain &nbsp;instead of the Source, like I initially did.<br /><br />&nbsp; &nbsp;However, this is not quite satisfactory to me. Simulations and common sense and also some more reading on the matter lead me to believe that the initial reverse engineered schematic might be wrong.<br />My initial hunch was that the schematic with Q4A, Q4B, Q5B and Q5C formed a complementary feedback pair. &nbsp;But the original schematic showed NPNs for Q5. Something did not add up.<br />&nbsp; &nbsp;So, from this, two conclusions may emerge:<br />&nbsp;- if indeed Q5 A and B are NPN, the they don't form a CFP with the FETs. The only other &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;explanation that comes to my mind is that they rather serve as a current source for the FETs. That sounds plausible, but that means that whoever did the reverse engineering &nbsp;goofed, which is kinda' hard to believe.<br />&nbsp;- however, were they to form a CFP, Q5 A and B would have to be PNPs, thus resulting in this schematic:<br /><br /><div class="separator" style="clear: both; text-align: justify;"><a href="https://4.bp.blogspot.com/-ocKSqN0Iv74/WXoY0jd5v1I/AAAAAAAADh8/5RbTGC0S-Ss0pCBHI3rmXx19EvJSBj_3ACKgBGAs/s1600/Diff_Probe_CFP.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="767" data-original-width="843" height="582" src="https://4.bp.blogspot.com/-ocKSqN0Iv74/WXoY0jd5v1I/AAAAAAAADh8/5RbTGC0S-Ss0pCBHI3rmXx19EvJSBj_3ACKgBGAs/s640/Diff_Probe_CFP.jpg" width="640" /></a></div><br />This is not much different from the initial one.<br /><br />&nbsp; &nbsp; I will do some proper investigation in the future to see what configuration actually behaves better, but for now, this will have to do, as I do not posess the gear to confirm or infirm any results from SPICE simulations.</div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com7tag:blogger.com,1999:blog-6412238293976072298.post-29939078096332368662015-09-22T13:37:00.000+03:002016-12-21T16:33:43.542+02:00How I make my PCBs: Toner transfer and PCB etching technique<div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; I know there's a ton of blogs and articles on the matter of DIY PCB making, and for every hundred articles, there's a hundred different ways to do it.&nbsp;</div><div style="text-align: justify;">So here, I'll just present you the way I do my PCBs. It's pretty simple and cost effective, not to mention I get good results...most of the time.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><span style="font-size: large;">Things needed:</span></div><ul style="text-align: justify;"><li>A4 Laminator (I use a <a href="https://www.google.ro/search?q=peach+laminator&amp;safe=off&amp;espv=2&amp;biw=1920&amp;bih=979&amp;source=lnms&amp;tbm=isch&amp;sa=X&amp;ved=0CAYQ_AUoAWoVChMIqL24vYyKyAIVglgUCh1mywsF#safe=off&amp;tbm=isch&amp;q=peach+PL718&amp;imgrc=_">Peach PL718</a>)</li><li>Glossy A4 paper (150 gramms)</li><li>Ferric chloride</li><li>A large glass bowl&nbsp;</li><li>An even larger plastic &nbsp;dish (for hot water)</li><li>Isopropanol alcohool</li><li>Plastic gloves</li><li>800 grit &nbsp;sandpaper (if needed)</li><li>Laser Printer</li></ul><div style="text-align: justify;">&nbsp; &nbsp;And now, how I use the above mentioned items. Well, first, it's important to have a flat &nbsp;laminator. Meaning that the paper, or in this case the PCB should go in and come out &nbsp;flat and not at an angle, because, for obvious reasons, the fiberglass material isn't all too "bendy".<br /><br /><div class="separator" style="clear: both;"><a href="http://4.bp.blogspot.com/-lO4v0_vJWag/VgWnB6UBYjI/AAAAAAAABPQ/-12uAwDPtjs/s1600/IMAG2473.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="425" src="https://4.bp.blogspot.com/-lO4v0_vJWag/VgWnB6UBYjI/AAAAAAAABPQ/-12uAwDPtjs/s640/IMAG2473.jpg" width="640" /></a></div>This is a recent board I did. It's about 300 mm in length, so heat dissipation can become an issue. </div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp;The paper I use is glossy 150 grams A4 paper. It can be of higher weight, maybe up to 250 grams, but the most important thing here is that the paper must be glossy. That will allow for all the toner to stick to the PCB and give you a nice solid transfer, that will not flake off when you remove the paper. Regular A4 paper just won't do. I've tried it, and the result is crap. The toner transferred to the PCB will be easily rubbed off with your fingers, if you use the regular paper.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp;So, needless to say, the next step is to use you PCB software to make your board design, the you print it out on a laser printer, on the mentioned type of paper. The type of toner is somewhat important, but most will give you a very decent result. Just do not forget to set your printer to print o heavy paper. This will have the effect of depositing a thicker amount of toner, which is exactly what you need.<br /><br /><div class="separator" style="clear: both;"><a href="http://4.bp.blogspot.com/-_Yl6b3UMKZI/VgWnBDgRjoI/AAAAAAAABRI/nmcZyaIQb04/s1600/IMAG2471.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="425" src="https://4.bp.blogspot.com/-_Yl6b3UMKZI/VgWnBDgRjoI/AAAAAAAABRI/nmcZyaIQb04/s640/IMAG2471.jpg" width="640" /></a></div><br /></div><div style="text-align: justify;">&nbsp; &nbsp;If the PCB has been lying around for a long time, in open air, it might have an oxide layer on it that will prevent the toner adhering. So I take some 800 grit sandpaper and give the copper a gentle rub. If you don't have any lying around, you could use some steel wool.<br />Then, wash the board under a stream of water then with some tissues soaked in isopropanol, give it another cleaning to get rid of the fine &nbsp;dust.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp;Next is setting things up for the toner transfer. As a common practice, I stick the paper to the PCB with a little Kapton tape so it doesn't wonder off when it goes through the laminator. I don't recommend using scotch tape or masking tape because the scotch tape will melt and ruin your day and the masking tape is too thick and any toner that is under that area will not be pressed down by the rollers of the laminator. Also, make sure the Kapton tape is in an area where there is no toner underneath, because of the same reason I mentioned for the masking tape.</div><div style="text-align: justify;">I make about 10 to 20 passes on the laminator, depending on the board size and level of details of the tracks (spacing and track width). I basically just go with my gut instinct, but a rule of thumb for me, is after the board gets up to temperature (the temperature where I need a glove to handle the board), I do about 6 or 7 more passes, then that's it.<br /><br /></div><div style="text-align: justify;">&nbsp; &nbsp;After it's cooled for a bit, I put the PCB with the stuck-on paper in some warm water and let it sit for 5 minutes. Then I peel most the paper off and the rest rub it off with my fingers or use a toothbrush. If &nbsp;the toner or the paper are not OK, this is where it shows. If you &nbsp;use the toothbrush, or just you fingers, no toner should flake off, even if you give it a firm rub. If it does, then either try another type of (glossy) paper or try with another laser printer.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-Tmvxxp31VNw/VgWnCeePJ5I/AAAAAAAABPc/TEG99eExJSk/s1600/IMAG2474.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://4.bp.blogspot.com/-Tmvxxp31VNw/VgWnCeePJ5I/AAAAAAAABPc/TEG99eExJSk/s400/IMAG2474.jpg" width="266" /></a></div></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-q4sMiN9FroE/VgWnCjiN2YI/AAAAAAAABRU/zL91YWDbpro/s1600/IMAG2475.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="https://2.bp.blogspot.com/-q4sMiN9FroE/VgWnCjiN2YI/AAAAAAAABRU/zL91YWDbpro/s400/IMAG2475.jpg" width="400" /></a></div>Don;t panic if yours looks like this under water. It's supposed to look like this. This has been staying in the water for&nbsp; a few minutes <br /><br /></div><div style="text-align: justify;">&nbsp; &nbsp;All you need to do now is etch away the copper. I use a "bain Marie" for this part. I put the ferric chloride in a glass bowl (this should be large enough to accommodate the PCB but not too large, because it will cause you to use too much etchant) and then I place this in a larger plastic dish full of hot water. Warm ferric chloride will work much faster than if you leave it at room temperature.</div><div style="text-align: justify;">Also, if you leave it to just sit, it will take a fairly long time for the whole copper to etch away, that's why I hold the glass bows in the water and constantly move it side to side (the idea is to keep the liquid moving in the glass dish).<br />In about 10 minutes, a &nbsp; 5cm x 5cm board should be ready. Don't forget to wear some plastic or latex gloves, because the etchant stains. And do this in a ventilated place, as the process will release Chlorine fumes. And Yes!, Chlorine is bad for you! - that's why they put it in water, to kill every living thing in there.<br /><br /></div><div style="text-align: justify;">&nbsp; &nbsp; After you can't see any more copper except the one covered by the toner, remove the board, wash the etchant off under &nbsp;a stream of water (again, careful here, because the ferric chloride stains you skin and anything else it touches ).&nbsp;</div><div style="text-align: justify;">After you admire you masterpiece and brag to anyone in the house at that moment, use a stainless steel sponge or steel wool to remove the toner off the copper. Again, do this under a stream of warm water. </div><div style="text-align: justify;">At the end you should be left with a nice, fresh PCB, ready for tinning and drilling some holes (if it's for Through-hole). I've tried this method for track widths down to 0.4 mm and it works great. You could push it down to 0.3 without any issue, but that depends on your luck and skill. Too much temperature and too much pressure may cause the narrower tracks to flatten out and actually get wider.</div><div style="text-align: justify;">Again, this is how I do things. It's worked so far, even for some SMD boards, but if you design a board with really fine pin pitch, I'd recommend the UV exposure method.<br /><br />It's OK if things don;t work out first go. As you can see below:<br /><br /><div class="separator" style="clear: both;"><a href="http://4.bp.blogspot.com/-FaUT1PPv4js/VgWnDglmACI/AAAAAAAABQo/kaK4F8SoUUo/s1600/IMAG2477.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-FaUT1PPv4js/VgWnDglmACI/AAAAAAAABQo/kaK4F8SoUUo/s640/IMAG2477.jpg" width="640" /></a></div><br />This is an example why the printer and toner a very important. Here, the printer did not deposit enough toner on the paper, even though the settings were for heavy paper. So it's all about experimenting, to find the right printer that works for you, or the right settings on a printer you already have.<br /><br />This is the second go, and the result is much better:<br /><br /></div><div style="text-align: justify;"><div class="separator" style="clear: both;"><a href="http://4.bp.blogspot.com/-J_4drXgQNNg/VgWnFZKWdiI/AAAAAAAABRc/6MDOzD-GwIU/s1600/IMAG2483.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="426" src="https://4.bp.blogspot.com/-J_4drXgQNNg/VgWnFZKWdiI/AAAAAAAABRc/6MDOzD-GwIU/s640/IMAG2483.jpg" width="640" /></a></div>&nbsp;&nbsp;&nbsp; The tracks did not flake off this time. Also, I had some 0.4mm tracks going extremely close&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; to some pads (upper right corner)...those turned out great.<br /><br />So the conclusion is, experiment, find what works for you, then stick with it.<br />Also, you might find that for through-hole boards that have thick traces, one process might apply, but for SMD boards, you might go with a UV exposure method maybe.<br /><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-82452100512035086032015-09-09T13:49:00.004+03:002015-09-09T13:49:41.117+03:00Updates and Things to come<div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Just thought I should give some updates on my current projects that I' working on right now.</div><div style="text-align: justify;"><br /></div><div>&nbsp; &nbsp; &nbsp;Currently I've bought an Arduino Mega for my <a href="http://electronicsplayground.blogspot.ro/2015/07/project-1.html">Voltcraft DPS 4005 PSU repair</a>&nbsp;and managed to wire everything up. I can now control the LCD as I wish, but currently struggling with getting the DAC to work. No matter how I drive the pins of the AD7541, I always get &nbsp;8.9 Volts on &nbsp;the output of the PSU. I thing there's something wrong with the pull-up resistors on &nbsp;the DAC pins. So next step is to remove those and see if I can drive the pins directly, with the Arduino. If this won't work, I have some more options I could try. On would be &nbsp;to install my own 12-bit DAC, although I wish it won't come to that.</div><div><br /></div><div>Also, I'm working on an USB Isolator based on the ADUM4160 from Analog Devices. I will make a post of the design process (schematic and PCB) for this thing where I'll also be stating the trouble I had with trying to get this thing to work reliably.</div><div><br /></div><div>And I've been wanting to do this for a while and it's taking some time to do right - How to design your &nbsp;own High-Voltage Differential Probe. This will be a two-part post. First I will talk about how I designed this thing, and what a differential probe is actually works, then, a future post will be of when I get the PCB &nbsp;done and try to test it out. That'll be a really nice one, you'll see.</div><div><br /></div><div>So, expect some really exciting stuff in the following weeks.&nbsp;</div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-2911203839034620522015-08-15T15:18:00.001+03:002015-08-24T09:54:11.281+03:00Accu-check Blood Sugar Meter Teardown<br /><div style="text-align: justify;">Today, on the chopping block&nbsp; we have an everyday (for some) medical equipment.&nbsp;</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-wCkPcsBNkgI/Vc8g09UZLFI/AAAAAAAABLU/1iD7FSIsVl8/s1600/152070-bloodglucosemeters-accuchek-compactplus.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="http://3.bp.blogspot.com/-wCkPcsBNkgI/Vc8g09UZLFI/AAAAAAAABLU/1iD7FSIsVl8/s320/152070-bloodglucosemeters-accuchek-compactplus.jpg" width="181" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-wCkPcsBNkgI/Vc8g09UZLFI/AAAAAAAABLM/muCSZwyeD6Y/s1600/152070-bloodglucosemeters-accuchek-compactplus.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a></div><br /><div style="text-align: justify;">&nbsp;It's the Accu-Check Compact blood sugar meter. I got this, for about 6 Euros, because I was interested in what' inside one of these and how such a device actually measures blood sugar. Also I had a hunch that it may have some niece electronics inside which I could use in some other projects.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Now, let's see what this baby looks like on the inside.</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-xN4wo9cvrX4/VcYiphe6jSI/AAAAAAAABGE/8E4KcSZTjEw/s1600/20150808_173034.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://2.bp.blogspot.com/-xN4wo9cvrX4/VcYiphe6jSI/AAAAAAAABGE/8E4KcSZTjEw/s400/20150808_173034.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-mkpdfgnfj8E/VcYipQiq6fI/AAAAAAAABDY/J1SaLN6jt84/s1600/20150808_173025.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://3.bp.blogspot.com/-mkpdfgnfj8E/VcYipQiq6fI/AAAAAAAABDY/J1SaLN6jt84/s400/20150808_173025.jpg" width="400" /></a></div><br /><div style="text-align: justify;">At first, doesn't seem like much, but things are really nice and compact inside. This is how it looks with the front off. The cavity on the right (Marked with blue) is where the drum of test strips goes in.</div><div style="text-align: justify;">A motorized rod (Marked with red) pushes a strip out of&nbsp; the drum and through the glucose sensor (Marked with purple)</div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-KHKrsHrc0yQ/Vc8kf7olNqI/AAAAAAAABLw/5Nhn3ILepXo/s1600/20150808_1730411.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="http://3.bp.blogspot.com/-KHKrsHrc0yQ/Vc8kf7olNqI/AAAAAAAABLw/5Nhn3ILepXo/s640/20150808_1730411.jpg" width="640" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Now, to detect glucose in the blood, there are two main ways.&nbsp;</div><div style="text-align: justify;">One is electrochemical in nature. You get the glucose in the blood to react to an agent on the test strip. Electrodes on the strip allow a bias voltage to be fed through and then&nbsp; the current is measured, which is proportional to the amount of glucose in the blood. The full scale current would be somewhere around&nbsp; 10-50 µA (<a href="http://www.maximintegrated.com/en/app-notes/index.mvp/id/4659">http://www.maximintegrated.com/en/app-notes/index.mvp/id/4659</a>)</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">The other way to do it is by optical measurement. When a blood sample is placed on the test strip, this will change color according to the glucose concentration. A LED diode biased with a known current is shone onto the test strip and a photo-diode senses the reflected light, who's intensity is dependent on the color of the strip. From what I've read, the biasing current is somewhere from 1µA to 5µA. This is the method also used in the Accu-Check Compact.</div><div class="separator" style="clear: both; text-align: center;"></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-6-ofjiQt3Fk/Vc8rffE1CWI/AAAAAAAABM4/CasTc8E48xM/s1600/20150808_180654.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="362" src="http://3.bp.blogspot.com/-6-ofjiQt3Fk/Vc8rffE1CWI/AAAAAAAABM4/CasTc8E48xM/s400/20150808_180654.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"></div><br /><div style="text-align: justify;">This is a close-up of the sensor. I've marked the window for the LED and photo-diode.</div><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-0V6qOfwk1G0/Vc8mRK-z84I/AAAAAAAABMM/FosAYARPDDM/s1600/20150815_134109.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://3.bp.blogspot.com/-0V6qOfwk1G0/Vc8mRK-z84I/AAAAAAAABMM/FosAYARPDDM/s400/20150815_134109.jpg" width="400" /></a></div><br />And this is the actual array, with the LED on the right and the photo-diode on the left.<br /><br />And not, let's see how the PCB for this thing looks like.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-Yjr_V2boX-o/VcYinqIzkVI/AAAAAAAABGE/H2VBVbDkScQ/s1600/20150808_172907.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="http://2.bp.blogspot.com/-Yjr_V2boX-o/VcYinqIzkVI/AAAAAAAABGE/H2VBVbDkScQ/s640/20150808_172907.jpg" width="640" /></a></div><br />Looks well made and designed. On the right, you can see the OLED display this thing uses. It's based on the <a href="https://www.crystalfontz.com/controllers/SSD1325_2.1.pdf">SSD1325</a> controller, for those that are wondering, so it should be relatively easy to take this out and use it for something else. The big black square on the PCB is actually a piezo-transducer, (<a href="http://www.edcon-components.com/Webside/LIE/500377/Originale/003-CSPT12B03-4.0F.pdf">Datasheet here</a>) for whatever sounds this thing makes.<br />A nice thing to notice are the multitude of test pads on the board. Being a medical device, probably there's a lot of things that need to be spot on for it to pass whatever standards that concern this specific field. Also, probably there's a bit of calibration going into this meter.<br /><br />There's also an infrared comm. port on this thing, probably for downloading all the history data onto a PC or something like that. Haven't tried playing with that, so I can't tell for sure, but from the manufacturer's data, that might indeed be the &nbsp;case.<br /><br />Also, after some searches, I found out that someone else took apart one of these glucose meters and hacked the display, which I'm going to do pretty soon. Information on that can be found here: <a href="http://home.arcor.de/wehrsdorf/Oled-Display-Recycling.html">http://home.arcor.de/wehrsdorf/Oled-Display-Recycling.html</a><br /><br />There's also a bit of grunt built into this meter, when it comes to processing power.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-y4mM9UI6VAc/VcYiot23flI/AAAAAAAABGE/KwFwdlLoMsA/s1600/20150808_172952.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://3.bp.blogspot.com/-y4mM9UI6VAc/VcYiot23flI/AAAAAAAABGE/KwFwdlLoMsA/s400/20150808_172952.jpg" width="400" /></a></div><br />That's most likely &nbsp;an ARM processor from Atmel, for the doing all the math and driving the infrared port and motors and whatever else on the board &nbsp;needs some &nbsp;smarts behind it. For the actual OLED display, there's an ATMEL Mega 168 micro, which I will soon acquaint myself with, in order to get the display going.<br /><br />What I was &nbsp;really curious about was &nbsp;the &nbsp;ADC that reads the photo-diode and also driver for the LED diode. From what I read, there must be some really precise measurements done in order to get accurate &nbsp;readings.<br /><br /><br /><br /><br /><br /><br /><br /><br /><a href="https://picasaweb.google.com/110876471461384099061/AccuCheckBloodSugarMeterTeardown?authuser=0&amp;feat=directlink">Link to Picasa Teardown Album</a>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-20573378667874710982015-07-22T22:37:00.002+03:002015-07-22T22:39:46.859+03:00What's this page about? Also first book recommendationMaybe some of you are wondering what's this doing here? What's up with this?<br /><br />Well, in this section, I'll be posting&nbsp; reference design books, service and user manuals for test gear that I own, schematics and so on, both to create a library of data for myself and also to maybe help others that are searching for ideas, manuals....<br /><br />So, let me start this off with a recommendation for those that are just starting with electronics and also for those that have the experience but never managed to read this book:<br /><br />"The Art of Electronics" by <span class="st">Paul Horowitz and Winfield Hill - Second Edition</span><br /><span class="st"><br /></span><span class="st">This is the go-to book if you're a student and also if you have some experience but having trouble with either understanding something or struggling with a design.</span><br /><span class="st">This edition is indeed old (1987-1988 I think) but most of it holds true even today, especially&nbsp; for the analog and linear chapters.</span><br /><span class="st"><br /></span><span class="st">I will not be making a review of this book because there are way too many out there. Having read it myself, I think it is essential that every electronics engineer try to go through this so one can gain a basic understanding of all things electronics. It is by no means complete, and again, it is very old, but hey, it's cheaper that the Third Edition (if you know where to download it from wink! wink!) and it'll keep you busy for quite a while.</span><br /><span class="st"><br /></span><span class="st">So, have fun reading, or just stay on this blog for a while longer and enjoy the eye candy.</span>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com1tag:blogger.com,1999:blog-6412238293976072298.post-30705713646956216012015-07-22T21:59:00.002+03:002015-07-22T22:02:24.269+03:00HP 3478A Multimeter Power Button Fix<div style="text-align: justify;">&nbsp;&nbsp; In the post about the <a href="http://electronicsplayground.blogspot.ro/2015/07/hp-3478a-multimeter-modifications.html">HP 3478A Multimeter Modification</a>, I said at one point that even though there's that issue about the stuck power switch, it doesn't bother me that much.</div><div style="text-align: justify;">Well, it turns out that it did bother me. In fact it was down right annoying. Most likely because of my O.C.D. was acting up, knowing that there's something not quite right about the multimeter.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, rummaging through my collection of old miscellaneous "things" I salvaged from different other devices people usually throw away (yes good people, sometimes,&nbsp; being a hoarder really pays off), I happened to find a spring power switch, which, in mind mind looked like a very good replacement for the one on the HP multimeter.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, I quickly took the top cover off my 3478A, had a quick peek at the broken power button, and indeed, looked very much like the one I recently found. So, I naturally thought "well, OK, I'll replace it now....how hard cand it be....should't take more than half an hour, right?" Famous last words.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Took me a few minutes to figure out just how to take apart the 3478A to get to the power button. First, the side plate had to be removed, exposing the cast aluminium frame.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-uZULVfD-3No/Va_TisU1t0I/AAAAAAAAA6o/rmdOE_Q7Yhc/s1600/IMAG2353.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://2.bp.blogspot.com/-uZULVfD-3No/Va_TisU1t0I/AAAAAAAAA6o/rmdOE_Q7Yhc/s400/IMAG2353.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, ignoring the very fashionable bed&nbsp; covers (that's how real engineers work....on beds and chairs&nbsp; and garages) the frame is held in place with four screws, one in each corner. Screwed to this frame piece is an aluminium plate that holds the transformer, a voltage regulator and also the infamous power switch.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">After first unscrewing the&nbsp; three bolts that hold the aluminium plate, I then undid the four corner screws and took off the frame piece.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;"></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-iloi20OVlS0/Va_TjYRKniI/AAAAAAAAA7E/wKhHGjkrBrs/s1600/IMAG2358.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://4.bp.blogspot.com/-iloi20OVlS0/Va_TjYRKniI/AAAAAAAAA7E/wKhHGjkrBrs/s320/IMAG2358.jpg" width="320" /></a></div><div style="text-align: justify;"></div><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-yanA8pY1tD8/Va_Tjbcc6aI/AAAAAAAAA9U/aMNgwmdBIuo/s1600/IMAG2356.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-yanA8pY1tD8/Va_Tjbcc6aI/AAAAAAAAA9U/aMNgwmdBIuo/s320/IMAG2356.jpg" width="320" /></a><a href="http://1.bp.blogspot.com/-sWTNmhWRGQo/Va_TkGPHIaI/AAAAAAAAA7U/3HaSJe8Px_w/s1600/IMAG2360.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-sWTNmhWRGQo/Va_TkGPHIaI/AAAAAAAAA7U/3HaSJe8Px_w/s320/IMAG2360.jpg" width="320" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Nope, still not there just yet. The screws that hold the power button are now accessible, but to get the whole power button out, the plate also has to come off. For this, the two screws that hold the transformer to the plate need to be&nbsp; taken out also. Only after this, can the aluminium plate be lifted, thus giving access to the button.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-aaxksgRdiZo/Va_TkqRyipI/AAAAAAAAA7s/DkGcUvteJio/s1600/IMAG2362.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://4.bp.blogspot.com/-aaxksgRdiZo/Va_TkqRyipI/AAAAAAAAA7s/DkGcUvteJio/s400/IMAG2362.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-HZM03Z2GzbE/Va_Tk24O8iI/AAAAAAAAA7c/w-W-_fRURLY/s1600/IMAG2363.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://3.bp.blogspot.com/-HZM03Z2GzbE/Va_Tk24O8iI/AAAAAAAAA7c/w-W-_fRURLY/s400/IMAG2363.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">If undertaking something of this sorts, take care how you handle the wires going to the regulator. Careful the solder doesn't crack or that you don't put too much stress on the wires themselves, because they might sometimes crack because of old age (although mine looked pretty good, despite the unit being&nbsp; built in 1991).</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">OK, pretty good so far. Now what?&nbsp; Well, take out the button, right? Out with the old, in with the new..er.</div><div style="text-align: justify;">I took my trusty needle nose pliers, grabbed the shaft of the button and pulled it apart from the lever of the button than protrudes out from the front panel.</div><div style="text-align: justify;">The, with a scalpel, I cut the shrink tube from around the power button and lo and behold...two capacitors and two resistors on the sides of the button...man, the guys at HP weren't stingy at all. Very nice bit of kit they built here. Annoying as hell because now I had to do even more work on it, but&nbsp; nice attention to detail.</div><div class="separator" style="clear: both; text-align: justify;"></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-lZJtHV6b-6A/Va_TlWemw3I/AAAAAAAAA78/orW45-ZUH9o/s1600/IMAG2366.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://1.bp.blogspot.com/-lZJtHV6b-6A/Va_TlWemw3I/AAAAAAAAA78/orW45-ZUH9o/s400/IMAG2366.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;"></div><div style="text-align: justify;">This is the part where I started to take the replacement button and measuring it up along side the original and see if it really fits....Well, not really. The shaft of the replacement is about 5 millimeters longer and&nbsp; it also had a much wider metal plate on the front.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-qLlQczar0-U/Va_TmXRxqdI/AAAAAAAAA8M/YkSyx85LjyI/s1600/IMAG2369.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://3.bp.blogspot.com/-qLlQczar0-U/Va_TmXRxqdI/AAAAAAAAA8M/YkSyx85LjyI/s400/IMAG2369.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">In the picture above you can see the solution. I took the metal bezel (front plate, call it what you will) from the original HP button and stuck it onto this. I don't know if it was divine intervention or just pure dumb luck, but somehow, I only has to file away about 1 millimeter so that the plate could snugly fit onto the new button. Also, in the picture above, you can see the original plate on the right, and the old plate already installed on the new button (new-ish, anyway).</div><div style="text-align: justify;">The next steps may sound straight forward, but it took me about 30 minutes to do. After filing away the shaft so it would fit into the lever and then cutting the lever about 5 millimeters and also the shaft of the button another 5 millimeters, I took off (no, not desoldered, but "took off", as in "cut off") the capacitors and resistors from the old switch and soldered them to the replacement one.</div><div style="text-align: justify;">The original HP switch was a&nbsp; Schadow,&nbsp; Type NE15, DPDT switch. The replacement was a&nbsp; DPST one, but that worked, since HP also used it in this configuration.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">A quick mockup seemed promising as the button and the lever seemed to fit and more importantly, actually worked.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">By the way, I didn't have shrink&nbsp; tube that large a diameter, so I put some electrical tape around the button to insulate it. May sound crude, may look even cruder, but it works and is also a very viable long term solution.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-fnxIIV0YNPo/Va_ToYYQvCI/AAAAAAAAA9A/uR6SrjafiH8/s1600/IMAG2374.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://4.bp.blogspot.com/-fnxIIV0YNPo/Va_ToYYQvCI/AAAAAAAAA9A/uR6SrjafiH8/s400/IMAG2374.jpg" width="400" /></a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">It may sound simple, all of this, but the whole taking the plate apart, figuring how to make the replacement button fit then soldering the wires and components to it, putting it back together, took a little over two hours.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, fun as it was, this is&nbsp; one of those things that you'd only do once. But at least, in the end, I now have a fully functioning multimeter.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-89651837045342097402015-07-14T21:36:00.002+03:002015-07-15T22:48:16.261+03:00HP 3478A Multimeter Modifications<div style="text-align: justify;">&nbsp;&nbsp;&nbsp; What kind of electronics engineer doesn't have a bench multimeter? Well, probably a lot, but since I didn't have any decent multimeter, aside from some very cheap UNI-T ones, I bought from eBay an old HP 3478A 5 1/2 digit multimeter.</div><div style="text-align: justify;">It'd old, I know, but it was "really cheap" (about 120 Euros) and only had some minor faults. I mean, what's a stuck Power button and a missing AMPs range fuse, right?<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-qg_urchU7Oc/VaZ0l31y-PI/AAAAAAAAA3Q/2x4Pdd_YQ54/s1600/IMAG2267.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="http://4.bp.blogspot.com/-qg_urchU7Oc/VaZ0l31y-PI/AAAAAAAAA3Q/2x4Pdd_YQ54/s320/IMAG2267.jpg" width="320" /></a></div></div><div style="text-align: justify;"><br />So, anyhow, it arrived, I was thrilled when I got it and surprise surprise, it worked surprisingly well and gave very accurate readings (tested it against another, borrowed, Fluke&nbsp; handheld multimeter and it was very accurate).<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-s3y6GvbX3J0/VaZ2MQz_C4I/AAAAAAAAA5A/ZIO5U3nP6NM/s1600/IMAG2288.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-s3y6GvbX3J0/VaZ2MQz_C4I/AAAAAAAAA5A/ZIO5U3nP6NM/s320/IMAG2288.jpg" width="320" /></a></div></div><div style="text-align: justify;">And, now what?&nbsp; Well, the Power button was stuck in the "On" position, which is very convenient, so for now, until I can get a replacement switch, I'll just have to unplug it when its job is done. (the button is&nbsp; all rusty and full of crud)<br /><br />I proceeded to put it through its paces and measured....stuff.&nbsp; I asked someone to lend me a Fluke DMM. Then, the rest was simple. For the&nbsp; DC volts, a home made, dual channel power supply,&nbsp; with 0-30 Volts on each channel proved very helpful and also a variable transformer for the AC volts helped, although, kind of tricky because the line voltage isn't really an ideal standard because of the constantly changing loading of the grid. The 2-wire and 4-wire Ohms also worked a treat.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">As for the missing AMPS fuse....This thing has plugs in the back also, right? Which I'm not going to use, right? So, why not disconnect the wire from the front AMPS plug, run a fuse and a wire to some other pug to the rear terminals and that's it. So I did just that. I ordered a fuse-holder and some 3A 250V fast fuses, cut the original Amps range wire,&nbsp; spliced it with the fuse holder and Voila! A fully functioning bench multimeter.<br /><br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-Kw7xAngyjYQ/VaZ1otWeZuI/AAAAAAAAA38/YwifhX7tJg4/s1600/IMAG2344.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://2.bp.blogspot.com/-Kw7xAngyjYQ/VaZ1otWeZuI/AAAAAAAAA38/YwifhX7tJg4/s320/IMAG2344.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-AK3m9Z3M11k/VaZ2JeDnxNI/AAAAAAAAA4s/uQX2PahQ1dI/s1600/IMAG2300.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-AK3m9Z3M11k/VaZ2JeDnxNI/AAAAAAAAA4s/uQX2PahQ1dI/s320/IMAG2300.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-C_T_6oUpiRo/VaZ1ppw0A7I/AAAAAAAAA30/A4gn-Np-Ftg/s1600/IMAG2348.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://4.bp.blogspot.com/-C_T_6oUpiRo/VaZ1ppw0A7I/AAAAAAAAA30/A4gn-Np-Ftg/s320/IMAG2348.jpg" width="320" /></a></div></div><div style="text-align: justify;">Also, if someone's curious, yes, I checked the battery for the ROM that holds the calibration data and it was either changed or still has some life in it, because it read about 3.6 Volts. <br /><br />Future thoughts&nbsp; - get a GPIB PCI card and start putting this little jewel to some good use in some automated tests for one of my projects I've been working on lately.<br /><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-40521545308063991082015-07-14T20:42:00.000+03:002015-07-23T19:30:15.204+03:00Teardown of an old russian C1-91 100 MHz, 2 Channel Oscilloscope<div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp;I got this <a href="https://picasaweb.google.com/110876471461384099061/C191OscilloscopeTeardown#6170656123980783458">old relic</a> for free from a very kind person, when I was still a student and working on my final year project. It's a great bit of kit, and, yes, it's a clone of the Tektronix modular scopes from the 80's, and yes, the labels are all in Russian, and yes, it takes 10 minutes for the CRT to actually show something....but hey, it did it's job.&nbsp;</div><div style="text-align: justify;">But now, since I&nbsp; got my new Rigol 1054Z and because the trigger on the old C1-91 has been trowing fits, I figured that it was just taking up space. Plus I just couldn't find a spot in a corner somewhere where it could sit undisturbed and hot have to move it every time I cleaned my room / lab, because this thing is heavy....about 30 kilograms worth. So I decided I could do without it and maybe use the components inside for other things, like an <a href="http://electronicsplayground.blogspot.ro/2015/07/project-2.html">oscilloscope clock</a> for example.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, taking after it's clone, the Tektronix 7000 series Mainframe oscilloscopes, it has three bays where one can mount different modules, from a <a href="https://picasaweb.google.com/lh/photo/zo7JAOM932Ee6VWBdqEcXdMTjNZETYmyPJy0liipFm0?feat=directlink">two channel oscilloscope input module</a>, to a <a href="https://picasaweb.google.com/lh/photo/WtP52rQh7t3We0x8l5h5vtMTjNZETYmyPJy0liipFm0?feat=directlink">multimeter module</a>, signal generator modules and so on. I removed mine, then proceeded to disassemble it to it's bare bones. Easier said that done, and I'll explain why.</div><div style="text-align: justify;">The people that designed this scope were either thinking, or blindly copied every detail from the Tektronix scopes. I, personally, since I haven't seen the insides of said Tektronox scopes, would like to believe the first option, that the russian&nbsp; engineers knew what they were doing.</div><div style="text-align: justify;">Because the frame of the scope was all aluminium, it only makes sense that to avoid corrosion pr oxidation, same metal fastners have to be used. Therefore, all the screws on the aluminium parts were also made of aluminium. Which would be nice, if they weren't made from the softest alloy they could find. And when I say soft, I mean that by applying a bit of force&nbsp; to loosen the Phillips head screws was enough to mangle them and so, be stuck in place.</div><div style="text-align: justify;">Oh well....where there's a hammer, there's a way.<br /><br />The first thing one notices when taking such&nbsp; devices apart is how different they look. Back then, the Russians made their own electronic components (capacitors, resistors, diodes, transistors of all kinds, ICs), after their own liking and in the process, developed a style of their own, to laying out boards. <br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-QnyyDzlw5ig/VaKTG6LA57I/AAAAAAAAAt0/y6IinCFi8Cg/s1600/20150607_200326.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://2.bp.blogspot.com/-QnyyDzlw5ig/VaKTG6LA57I/AAAAAAAAAt0/y6IinCFi8Cg/s400/20150607_200326.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-dkK5EWEdb1Y/VaKTLO4NYpI/AAAAAAAAAwo/ZgmSg8M804A/s1600/20150607_200527.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://1.bp.blogspot.com/-dkK5EWEdb1Y/VaKTLO4NYpI/AAAAAAAAAwo/ZgmSg8M804A/s400/20150607_200527.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-L1ZOLIMHews/VaKTO55HbMI/AAAAAAAAAv8/G98JiVm2ddI/s1600/20150607_204747.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://3.bp.blogspot.com/-L1ZOLIMHews/VaKTO55HbMI/AAAAAAAAAv8/G98JiVm2ddI/s400/20150607_204747.jpg" width="400" /></a></div>&nbsp; <br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-Lur27mnKDvg/VaKTIvYAgKI/AAAAAAAAAwo/xhhCv_C44ns/s1600/20150607_200410.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="http://4.bp.blogspot.com/-Lur27mnKDvg/VaKTIvYAgKI/AAAAAAAAAwo/xhhCv_C44ns/s400/20150607_200410.jpg" width="400" /></a></div><br />See what I mean. By the way, the square metal cans are actually hybrid circuits.<br />Trust me when I say it's weird. And don't even get me started on the schematic.&nbsp;In fact, as I'm&nbsp; writing this, I'm trying to figure out the schematics for this thing, so that I can turn it into&nbsp; a prototype for an oscilloscope clock and sincerely, not getting anywhere with it. I mean, they have all kinds of numbered wires going all over the place to numbered connectors. But the same wire has different markings on each end and each pair of connectors (from one board to another) also have different names, making things very frustrating and hard to read. A post with my efforts on the scope clock will follow at some point.<br /><br />Until then, I leave you with the <a href="https://picasaweb.google.com/110876471461384099061/C191OscilloscopeTeardown?authuser=0&amp;feat=directlink">Picasa album with teardown pictures</a> for this thing so you can admire this in its full glory and actually get a feel for how bulky this thing is and feels.<br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com2tag:blogger.com,1999:blog-6412238293976072298.post-77217777026817724982015-07-02T21:04:00.003+03:002015-07-16T23:13:01.903+03:00Teardown of old NEC MultiSync MT Projector<div style="text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A few months ago I got my hands on an <a href="https://picasaweb.google.com/110876471461384099061/NECTeardown?authuser=0&amp;feat=directlink" target="_blank">old NEC Projector</a> from the local flea market for almost nothing (20 Euros or so).</div><div style="text-align: justify;">Of course, after carrying up the stairs to my apartment, which is no mean feat, because this thing weighs about 30 kilos, I followed the normal procedure for such a nice piece of old "vintage" electronic gear, which was to stand back and admire it. Ain't she a beaty?<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-vUM0HMrWrro/U8VUIuvKcrI/AAAAAAAAAbo/iTt4FyObQ8Y/s1600/IMAG1208.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-vUM0HMrWrro/U8VUIuvKcrI/AAAAAAAAAbo/iTt4FyObQ8Y/s320/IMAG1208.jpg" width="320" /></a></div><br />&nbsp;After getting my trusty screwdriver set out, first I wanted to see the lamp in this thing. Pretty ordinary for it's day, but what really surprised me was that it probably had been recently replaced - or so it said in the menu. Only <a href="https://picasaweb.google.com/lh/photo/OQt4ZiM4-I2KEByrDyghrdMTjNZETYmyPJy0liipFm0?feat=directlink">600 hours</a> of run-time? What a score.<br /><br />So why take apart a perfectly functional projector? Well, for one, the 640x480 maximum resolution this thing has isn't really of much use....for anything. Another reason is that it has lots of nice components which are worth much more than what I pain for it. But the main reason is curiosity. I just want to rip it open then drool over it while I try and figure out what everything does.<br /><br />So,&nbsp; first thing, <a href="https://picasaweb.google.com/lh/photo/3GHE0l5ZHnFTzX9VOlVARtMTjNZETYmyPJy0liipFm0?feat=directlink">the lamp</a>. Looks nice an beefy, and really nice thing that the <a href="https://picasaweb.google.com/lh/photo/-v91T8nrH1WI7J4jvUKQdtMTjNZETYmyPJy0liipFm0?feat=directlink">High Voltage power supply</a> for this works independently of the projector's "mother board". Of course I couldn't resist not playing with it.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-v_hYL-zgKqc/U8VVtjIFAnI/AAAAAAAAAbo/J1WyDTjfkrM/s1600/IMAG1390.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://4.bp.blogspot.com/-v_hYL-zgKqc/U8VVtjIFAnI/AAAAAAAAAbo/J1WyDTjfkrM/s320/IMAG1390.jpg" style="cursor: move;" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-W5kksQR8A6o/U8VVuOm_eEI/AAAAAAAAAbo/Cx1KoqWDXBw/s1600/IMAG1391.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://4.bp.blogspot.com/-W5kksQR8A6o/U8VVuOm_eEI/AAAAAAAAAbo/Cx1KoqWDXBw/s320/IMAG1391.jpg" width="320" /></a></div><br /><br /><br />Top notch job on this. Looks like the engineers that worked on this design did a really nice job. I mean, it did cost about 10.000 dollars new....back in the 90's.<br />In fact, this entire thing was really nicely engineered and&nbsp; with quality parts. Rubycon and Nichicon caps, Omron relays, really nice BNCs and connectors on the front. And also, a ton of quality optics in it.<br /><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-GMakdxJlFcQ/U8VVgLhWz6I/AAAAAAAAAbo/UvhFQVA7eJg/s1600/IMAG1369.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://4.bp.blogspot.com/-GMakdxJlFcQ/U8VVgLhWz6I/AAAAAAAAAbo/UvhFQVA7eJg/s320/IMAG1369.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-uNDiOSNwdvk/U8VVgznJThI/AAAAAAAAAbo/EW4er4Ge9go/s1600/IMAG1370.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://3.bp.blogspot.com/-uNDiOSNwdvk/U8VVgznJThI/AAAAAAAAAbo/EW4er4Ge9go/s320/IMAG1370.jpg" width="320" /></a></div></div><div style="text-align: justify;"><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-v5lYW-qIqeg/U8VmRHvsnrI/AAAAAAAAAbo/8W3g2RVwJbk/s1600/IMAG1425.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-v5lYW-qIqeg/U8VmRHvsnrI/AAAAAAAAAbo/8W3g2RVwJbk/s320/IMAG1425.jpg" width="320" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-PiaG_nmjyyk/U8VmLIK24CI/AAAAAAAAAbo/x0FfQ3RY9Co/s1600/IMAG1414.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://1.bp.blogspot.com/-PiaG_nmjyyk/U8VmLIK24CI/AAAAAAAAAbo/x0FfQ3RY9Co/s320/IMAG1414.jpg" width="320" /></a></div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (FYI:That's in centimeters, not inches)<br /><br /><br />After making my way through the jungle of wires inside this thing, I finally got to the <a href="https://picasaweb.google.com/lh/photo/acgaIoxy4Xd3w5uoWoEHcNMTjNZETYmyPJy0liipFm0?feat=directlink">main power board</a>. As I said, really nice design. No cheap Wan-Hung-Lo brand caps here, thank you very much.<br />Input filter, MOVs, this thing's got it all.<br />The board is mainly dedicated to the switch-mope supply, but there's also a smaller transformer, probably powering the analog part of the <a href="https://picasaweb.google.com/lh/photo/hYI6Sa-fs5Jr1Kc0mualbdMTjNZETYmyPJy0liipFm0?feat=directlink">main logic board</a> i.e the op-amps for the video output.<br />Also, notice the amount of EMI suppression this board has on it (especially the analog section), and also&nbsp; the forest of electrolytics scattered all over.</div><div style="text-align: justify;"><br />It took me the better part of a day to get to the metal chassis for the optics&nbsp; of the projector. Everything was either&nbsp; tied down with cable ties&nbsp; or screwed to something. Like I said...quality.<br />But once I got to the optics....<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-xiBu3gSJNpA/U8VmJOHzvBI/AAAAAAAAAbo/MbW-EP5OHPo/s1600/IMAG1408.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="http://3.bp.blogspot.com/-xiBu3gSJNpA/U8VmJOHzvBI/AAAAAAAAAbo/MbW-EP5OHPo/s320/IMAG1408.jpg" width="320" /></a></div><br />I spent another day carefully getting every mirror out and the trying to figure out how this thing actually produced an image.<br />And this is what I came up with:<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-yQLHSYgz2Qk/U8VVyB_s3CI/AAAAAAAAAbo/SfYxxKa-YVo/s1600/IMAG1397.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="266" src="http://2.bp.blogspot.com/-yQLHSYgz2Qk/U8VVyB_s3CI/AAAAAAAAAbo/SfYxxKa-YVo/s400/IMAG1397.jpg" width="400" /></a></div><br />Excuse the hand drawn schematic, but I really suck when it comes to expressing my inner artist.<br />Basically, the light from the lamp is split into three optical pathways, each corresponding to the colors&nbsp; Cyan, Magenta and Yellow. This is done with two dichroic mirrors. For those that don't know what a dichroic mirror is (don't worry, I didn't&nbsp; know either before this teardown), it's a mirror that only reflects a certain wavelength of light, while letting the rest of the spectrum to freely pass through it without much disturbance (i.e. reflections or refractions).<br />There are also two other "normal" mirrors that are there only to help guide the light to the&nbsp; main&nbsp; objective.<br />Now, after the colors have been separated, the image has to be produced somehow. This is where three LCD displays come in. The video data is taken from the input panel,&nbsp; then the processor&nbsp; splits that up into three colors, then sends each color channel data to the <a href="https://picasaweb.google.com/lh/photo/qvzvLM6NiIGw0pRb904WEtMTjNZETYmyPJy0liipFm0?feat=directlink">LCDs</a>. The LCDs are almost transparent (they have a darkish tinge to them) so some&nbsp; light is lost at this stage. Also, in front of two of the LCDs there are polarizing filters - one vertical and the other horizontal. I haven't quite figured this part out yet, I don't know how they tie up in the final image.<br />From here on, all that;s left to do is join the three optical path with some clever use of optics into one beam, then send it on it's way to be projected on to whatever surface&nbsp; someone desires (as long as it's white).<br /><br />Now, I'd like to mention that although it's much nicer for the eye to have this kind of splitting of the video data into three separate&nbsp; colors, it's expensive as you need a lot of quality optics. Also there is a lot of light lost because the dichroic mirrors do not reflect 100% of the light and because the LCDs are somewhat dark, so the final image looks really dim. So a lot of light is needed to be pumped into this thing to get&nbsp; a relatively ok picture on the other end.<br />So, that's why we're stuck with the color wheel in today's projectors that make you see stars every time you rapidly move your eyes when looking at a modern projector (or should I say the image projected by it)<br /><br />If you would like to know more about the color wheel I mentioned, <a href="https://www.youtube.com/watch?v=9nb8mM3uEIc">watch this video</a> that Ben Krasnow made, detailing how modern projectors work. It's worth it, trust me.<br /><br />For more information on this projector, you can visit: http://www.projectorcentral.com/NEC-MultiSync_MT.htm</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-23119126456902482902015-07-02T21:01:00.002+03:002015-07-14T20:45:15.965+03:00Oscilloscope ClockRazvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com0tag:blogger.com,1999:blog-6412238293976072298.post-65937928028020981012015-07-02T21:00:00.003+03:002015-08-11T19:08:00.316+03:00Repair of Voltcraft DPS-4005PFC Power Supply - Part 1<div style="text-align: justify;"><br /></div><div style="text-align: justify;">&nbsp; &nbsp; </div><div style="text-align: justify;">&nbsp; &nbsp; &nbsp; &nbsp; About a year ago I bought and old <a href="https://picasaweb.google.com/110876471461384099061/VoltcraftDPS4005PFC?feat=directlink" target="_blank">Voltcraft DPS-4005PFC</a> &nbsp;adjustable switchmode power supply, advertised as not working. It was missing the main controllers and also the two main switching transistors, but I thought I would give it a shot. I mean, if all else failed, I could rip out the rest of the bits in it and spin my own PSU.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">I thought it was a nice bit of kit: 0-40 Volts and 0-5 Amps, PFC, a nice big LCD....</div><div style="text-align: justify;">When I got it, I gave it a thorough visual &nbsp;inspection and the once-over with the DMM, to check for any burnt or missing components.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">After it all checked out, I put it on a shelf somewhere, waiting to buy some 2SC2625 for it and see if it did anything (besides blowing up in my face).</div><div style="text-align: justify;">A moth ago, I decided to buy the transistors. Got them, soldered them in, now, to test it.....But how?</div><div style="text-align: justify;">Well, Arduino was the answer, of course.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="266" src="http://1.bp.blogspot.com/-_la-aEaScYA/VaZ2U13H3nI/AAAAAAAAA5k/2heyQdtapyM/s400/IMAG2298.jpg" width="400" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">I got the <a href="https://drive.google.com/file/d/0BxilARsN_3FqUWxNbTl4WWE2eEk/view?usp=sharing" target="_blank">schematics</a> out, identified the pins for the &nbsp;AD7541 DAC, wrote a quick and dirty code for it, and voila!, voltages on the output. Perfect.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Now, let's get the whole thing working. I mean the LCD, the rotary encoder, the buttons. the current limiting, the fan and, apparently, the fine voltage setting mode this thing has (I'll talk about this later)</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, back to the schematics. This thing used two micro-controllers to drive this thing. A Windbond W78C32B-40 &nbsp;to drive the LCD and do some EEPROM storage &nbsp;and an &nbsp;Atmel AT89C51 to do the rest of the control and housekeeping. So the Leonardo that I have hooked up to this thing &nbsp;isn't going to cut it. The plan is to get all the parts working, one by one, then buy a Mega and put it all together, into one code and fire this thing up (figuratively speaking, of course).</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Just to see what it takes to drive this thing, below is a table with all the connections I need to hook up to get the PSU into working shape.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="640" src="http://4.bp.blogspot.com/-Cgoe7f6DiOw/VcH6KHjvXKI/AAAAAAAAA-M/Zapp2MQDnDw/s640/Table.jpg" width="355" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">The pin assignment&nbsp; on the Mega is mostly chosen randomly, so they will probably change by the time I get it into final shape.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">So, let's get to the interesting part. First off&nbsp; is the &nbsp;encoder and output relay. Simple things.</div><div style="text-align: justify;">For the encoder, I used the library from&nbsp; <a href="https://www.pjrc.com/teensy/td_libs_Encoder.html">this site</a>. It's very easy ans simple to use and it worked first time, without any headaches.</div><div style="text-align: justify;">Next, was the LCD. Boy, did that ever got me frustrated. It's simple, if you read the datasheet, but who has time for that. The chipset for the LCD is the <a href="http://www.nxp.com/documents/data_sheet/PCF8576.pdf">PCF8576</a>.</div><div style="text-align: justify;">I did a quick search for anyone else thet had to deal with this controller, and there were some references and some code available, so I didn't had to start from scratch.</div><div style="text-align: justify;">&nbsp;It's nice that it's an I2C device, so it was easy to wire in (of course I mixed up the SDA and SCL pins the first time)</div><div style="text-align: justify;">Because the LCD has 4 backplanes, the setup for this LCD is 1:4 drive mode, with 1/3 bias configuration. That means, that if you start sending it data starting from address 0x00 (B00000000), each consecutive byte of data will increase the address&nbsp; counter in the PCF8576 by 2. This took me a while to get used to. Also, I made it more complicated because I actually wanted to understand how this thing works, so I got out an A3 paper, made a copy of the LCD segments on it and started feeding it address and data bytes (please excuse the bad hand writing).</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="266" src="http://3.bp.blogspot.com/-1s9YkUBYP00/VaVG4uL292I/AAAAAAAAAx4/guIpbw_gf7I/s400/IMAG2320.jpg" width="400" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">At first, I had no clue what I was doing and luck would have it, I started with an odd address value, which gave me the weirdest results: a byte controlled the segments on half a digit and half on the adjacent digit.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="266" src="http://4.bp.blogspot.com/-Du_62N3NwUk/VaVG3_7PmlI/AAAAAAAAAyE/picT4dBbH3Y/s400/IMAG2317.jpg" width="400" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">After a few frustrating hours, I eventually got fed up with this, started from address B00000000 and fed it about 20 bytes of data and lo and behold, the whole LCD lit up, AWESOME!</div><div style="text-align: justify;">An hour later I had all the individual LCD segments mapped out.</div><div style="text-align: justify;"><br /></div><div class="code" style="text-align: justify;">#include &lt;Wire.h&gt;<br /><br />#define ADDRESS&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B0111000&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //&nbsp; I2C Address of PCF8576<br />#define DEVICE_SELECT&nbsp;&nbsp;&nbsp; B11100000&nbsp;&nbsp;&nbsp; //&nbsp; Device select&nbsp;&nbsp; [Command]&nbsp;&nbsp;&nbsp; [1100]&nbsp;&nbsp;&nbsp; [A2 A1 A0]<br />#define MODE_SET&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B11001000&nbsp;&nbsp;&nbsp; //&nbsp; MODE SET&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; [C]&nbsp;&nbsp; [10]&nbsp;&nbsp; [LowPower]&nbsp;&nbsp; [Enable]&nbsp;&nbsp; [Bias]&nbsp;&nbsp; [Mux]<br />#define BANK_SELECT&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B11111000&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //&nbsp; no effect in 1:4 multiplex mode<br /><br />unsigned long time;<br />unsigned long time_now;<br /><br />void setup()<br />{&nbsp; <br />}<br />void loop()<br />{<br />&nbsp; Wire.begin(); // join i2c bus (address optional for master)<br />&nbsp;&nbsp; delay(1000); //allow lcd to wake up<br />&nbsp; Wire.beginTransmission(ADDRESS);&nbsp; //adress the upper I2C-controller.<br />//&nbsp; delay(2);<br />&nbsp; Wire.write(MODE_SET);&nbsp; //MODE SET (Command)(10)(LowPower)(Enable)(Bias)&nbsp; (Mux)<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (0)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (1)&nbsp;&nbsp;&nbsp;&nbsp; (ΩBias) (1:2)<br />&nbsp; Wire.write(DEVICE_SELECT);&nbsp; //Device select (Command)(1100)(A2 A1 A0)<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (0&nbsp; 0&nbsp; 0 )<br />Wire.write(BANK_SELECT);&nbsp; //Bank Select (Command)(11110)(Input)(Output)<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (0)&nbsp;&nbsp;&nbsp; (0)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <br />&nbsp; Wire.write (B00000000) ;&nbsp; //Address - starts gro 0x00<br />&nbsp; Wire.write (B11111011) ; //5 and limits and dots and Output//A-0<br />&nbsp; Wire.write (B11111111) ;//6 and i-const //A-2<br />&nbsp; Wire.write (B11111111) ;//9 and remote //A-4<br />&nbsp; Wire.write (B11111111) ;//10 and locked //A-6<br />&nbsp; Wire.write (B11111011) ;//11 and p-const //A-8<br />&nbsp; Wire.write (B11111010);//12 and W //A-10<br />&nbsp; Wire.write (B00000000); //Overtemp, ON, 18 and 19 //A-12<br />&nbsp; Wire.write (B11011011);//20 and w // A-14<br />&nbsp; Wire.write (B11111100);//18 and 19 // A-16<br />&nbsp; Wire.write (B11110110); // Off, 15 and 16 // A-18<br />&nbsp; Wire.write (B11101011);//17 and a // A-20<br />&nbsp; Wire.write (B11111011);//15 and 16 // A-22<br />&nbsp; Wire.write (B11111011);//14 and v // A-24<br />&nbsp; Wire.write (B11111011); //13 //A-26<br />&nbsp; Wire.write (B11111011);//4 and V // A-28<br />&nbsp; Wire.write (B11111011); //3 and up arrow // A-30<br />&nbsp; Wire.write (B11111011); //2 and down arrow // A-32<br />&nbsp; Wire.write (B11011101); // 1 and fine // A-34<br />&nbsp; Wire.write (B11111011); //8 and A // A-36<br />&nbsp; Wire.write (B10111011); //7 and u-const // A-38<br />Wire.endTransmission();<br />} </div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">I've put comments next to each data byte regarding what digit number o character they encode, after my own notation, of course. Here are the pics with the corresponding character numbering:</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="180" src="http://3.bp.blogspot.com/-pgLq71thJ98/VcYBZdI47nI/AAAAAAAABBc/mHIqkicXLw4/s320/20150808_160408.jpg" width="320" /> </div><div class="separator" style="clear: both; text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="180" src="http://4.bp.blogspot.com/-e9Cf7KGRBmM/VcYBZWVkGJI/AAAAAAAABBg/j3mt4FNrPYE/s320/20150808_160358.jpg" width="320" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;"></div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;"></div><div style="text-align: justify;">There are two mappings because I've split up the screen into two areas so I would have more space on a single A4 paper. The first pic is of the left side of the display, where the main voltage, current and power reading are displayed and also other characters&nbsp; like the "Limits", "V", "A", "W" characters, etc.</div><div style="text-align: justify;">The second pic is of the right side of the display, with the limits settings. Underneath each digit or character is the number I assigned to it and corresponds to the numbers in the Arduino code.</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="213" src="http://4.bp.blogspot.com/-LZBjToC_53M/VaVG5QSn_cI/AAAAAAAAAyA/rpqTDAO1bn8/s320/IMAG2321.jpg" width="320" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Looks better now, doesn't it?&nbsp; And yes, it was supposed to look like that i.e. "6"s and inverted "A"s.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">And now a quick explanation of how the bits map out in a byte.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Say you have:</div><div style="text-align: justify;"><br /></div><div class="separator" style="clear: both; text-align: justify;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img border="0" height="41" src="http://3.bp.blogspot.com/-QJTR8cooUsU/VcoaIf7aUkI/AAAAAAAABKE/1yo4R4oDPOc/s400/LCD%2BAddress.jpg" width="400" /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">The address is 0x22 which is 32 in decimal. The bits from 0 to3 and 5 to 7 map out segments of a digit (in this case digit 1) while the 4th bit is for a character on the screen (in this case&nbsp; "Fine")</div><div style="text-align: justify;">So, at address 0x22, bit 0 set to "1" turns on segment D of digit 1 (which according to my hand drawn diagram of the LCD is the left most digit on the first row). Bit 4 set to "1" will turn on the "Fine" symbol and bit 7 set to "1" will turn on segment B of digit 1.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Hope this makes some sense. If not, you can always leave a comment or contact me via my Facebook page: <a href="https://www.facebook.com/ElectronicsPlayground?ref=hl">https://www.facebook.com/ElectronicsPlayground?ref=hl</a></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;">Also, there's going to be some updates coming, once I&nbsp; put everything together on the Arduino Mega and move the actual code on it.</div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div><div style="text-align: justify;"><br /></div>Razvan Caldararuhttps://plus.google.com/110876471461384099061noreply@blogger.com2